asp.net mvc - MVC 4.0 String was not recognized as a valid Boolean -

i have razor 2.0 form works locally. i've verified dll's on prod mvc, razor, , helpers latest version. i'm getting exception on every page uses @html.beginform varying parameters. mvc pages seem work fine long no form helpers used:

exception:            [formatexception: string not recognized valid boolean.]                system.boolean.parse(string value) +13981920                system.convert.changetype(object value, type conversiontype, iformatprovider       provider)     +811                system.web.mvc.viewcontext.scopeget(idictionary`2 scope, string name, tvalue      defaultvalue) +89                system.web.mvc.scopecache..ctor(idictionary`2 scope) +75                system.web.mvc.scopecache.get(idictionary`2 scope, httpcontextbase httpcontext) +299                system.web.mvc.viewcontext.getclientvalidationenabled(idictionary`2 scope,      httpcontextbase               httpcontext) +9                 system.web.mvc.html.formextensions.formhelper(htmlhelper htmlhelper, string formaction,      `enter code here`formmethod method, idictionary`2 htmlattributes) +233                system.web.mvc.html.formextensions.beginform(htmlhelper htmlhelper, string actionname,      string controllername, formmethod method, object htmlattributes) +134                asp._page_views_portal_loginform_cshtml.execute() in      e:\webroot\nw_qa_bleedhr\views\portal\loginform.cshtml:4                system.web.webpages.webpagebase.executepagehierarchy() +280                system.web.mvc.webviewpage.executepagehierarchy() +125                system.web.webpages.webpagebase.executepagehierarchy(webpagecontext pagecontext,      textwriter writer, webpagerenderingbase startpage) +196                system.web.mvc.html.partialextensions.partial(htmlhelper htmlhelper, string      partialviewname, object model, viewdatadictionary viewdata) +147                asp._page_views_portal_welcome_cshtml.execute() in      e:\webroot\nw_qa_bleedhr\views\portal\welcome.cshtml:9                system.web.webpages.webpagebase.executepagehierarchy() +280                system.web.mvc.webviewpage.executepagehierarchy() +125                system.web.webpages.startpage.executepagehierarchy() +143                system.web.webpages.webpagebase.executepagehierarchy(webpagecontext pagecontext,      textwriter writer, webpagerenderingbase startpage) +181                system.web.mvc.viewresultbase.executeresult(controllercontext context) +380                system.web.mvc.<>c__displayclass1a.<invokeactionresultwithfilters>b__17() +33                system.web.mvc.controlleractioninvoker.invokeactionresultfilter(iresultfilter filter,      resultexecutingcontext precontext, func`1 continuation) +613                system.web.mvc.controlleractioninvoker.invokeactionresultwithfilters(controllercontext      controllercontext, ilist`1 filters, actionresult actionresult) +263                system.web.mvc.async.<>c__displayclass25.<begininvokeaction>b__22(iasyncresult      asyncresult) +240                system.web.mvc.<>c__displayclass1d.<beginexecutecore>b__18(iasyncresult asyncresult) +28                system.web.mvc.async.<>c__displayclass4.<makevoiddelegate>b__3(iasyncresult ar) +15                system.web.mvc.controller.endexecutecore(iasyncresult asyncresult) +53                system.web.mvc.async.<>c__displayclass4.<makevoiddelegate>b__3(iasyncresult ar) +15                system.web.mvc.<>c__displayclass8.<beginprocessrequest>b__3(iasyncresult asyncresult) +42                system.web.mvc.async.<>c__displayclass4.<makevoiddelegate>b__3(iasyncresult ar) +15                system.web.callhandlerexecutionstep.system.web.httpapplication.iexecutionstep.execute()      +606                system.web.httpapplication.executestep(iexecutionstep step, boolean&      completedsynchronously) +288 

this form dead simple:

@model gis.pangea.nw.presentation.viewmodels.loginview <div id="doalogin_div">     @using (html.beginform("candidatelogin", "account", formmethod.post, new { id = "loginform" }))    {         @html.antiforgerytoken()         @html.validationsummary()          <table id="loginform_tb">             <tr>                 <td colspan="2" id="loginheader_td">                     <h3 id="loginheader_h3">@model.returningapplicanttext</h3>                 </td>             </tr>             <tr>                 <td class="fieldname_td" id="username_td">                     @html.labelfor(p=>model.logindto.username)                 </td>                 <td class="fielddata_td" id="usernameinput_td">                     @html.textboxfor(p => model.logindto.username, new {id="username",name="username" })                     @html.validationmessage("username")                 </td>             </tr>             <tr>                 <td class="fieldname_td" id="password_td">                     <label for="password">                         @html.encode(model.passwordtext)                     </label>                 </td>                 <td class="fielddata_td" id="passwordinput_td">                     @html.passwordfor(p=>model.logindto.password,  new {id="password",name="password" })                     @html.validationmessage("password")                 </td>             </tr>             <tr>                 <td colspan="2" id="forgotpassword_td">                     @html.actionlink("forgot username or password?","forgotpassword")                 </td>             </tr>             <tr>                 <td colspan="2" id="loginsubmit_td" class="submit_td">                     <input type="submit" class="formbutton" value="@model.loginbuttontext" />                 </td>             </tr>             <tr>                 <td colspan="2" id="loginvalidation_td">                     @if (!string.isnullorempty(model.logindto.validationmessage))                     {                         <span class="validationmessage">@model.logindto.validationmessage</span>                     }                 </td>             </tr>         </table>     } </div> 

i suspected wrong or missing version of dll. mvc components should in bin folder, , i've verified (at least top level dlls)

here view config file:      <?xml version="1.0" encoding="utf-8"?>     <configuration>       <configsections>         <sectiongroup name="system.web.webpages.razor" type="system.web.webpages.razor.configuration.razorwebsectiongroup, system.web.webpages.razor, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35">           <section name="host" type="system.web.webpages.razor.configuration.hostsection, system.web.webpages.razor, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" requirepermission="false" />           <section name="pages" type="system.web.webpages.razor.configuration.razorpagessection, system.web.webpages.razor, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" requirepermission="false" />         </sectiongroup>       </configsections>       <system.web.webpages.razor>         <host factorytype="system.web.mvc.mvcwebrazorhostfactory, system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" />         <pages pagebasetype="system.web.mvc.webviewpage">           <namespaces>             <add namespace="system.web.helpers" />             <add namespace="system.web.mvc" />             <add namespace="system.web.mvc.ajax" />             <add namespace="system.web.mvc.html" />             <add namespace="system.web.optimization" />             <add namespace="system.web.routing" />             <add namespace="mvccontrolstoolkit.core" />             <add namespace="mvccontrolstoolkit.controls" />             <add namespace="mvccontrolstoolkit.controls.validation" />           </namespaces>         </pages>       </system.web.webpages.razor>       <appsettings>         <add key="webpages:enabled" value="false" />       </appsettings>       <system.web>         <compilation debug="false" targetframework="4.5">           <assemblies>             <add assembly="system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" />             <add assembly="system.web.webpages, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" />             <add assembly="system.web.helpers, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" />             <add assembly="system.web.webpages.razor, version=2.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" />           </assemblies>         </compilation>         <httphandlers>           <add path="*" verb="*" type="system.web.httpnotfoundhandler" />         </httphandlers>         <pages validaterequest="false" pageparserfiltertype="system.web.mvc.viewtypeparserfilter, system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" pagebasetype="system.web.mvc.viewpage, system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" usercontrolbasetype="system.web.mvc.viewusercontrol, system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35">           <controls>             <add assembly="system.web.mvc, version=4.0.0.0, culture=neutral, publickeytoken=31bf3856ad364e35" namespace="system.web.mvc" tagprefix="mvc" />           </controls>         </pages>       </system.web>       <system.webserver>         <validation validateintegratedmodeconfiguration="false" />         <handlers>           <remove name="blockviewhandler" />           <add name="blockviewhandler" path="*" verb="*" precondition="integratedmode" type="system.web.httpnotfoundhandler" />         </handlers>       </system.webserver>     </configuration>   project uses combination of asp pages , mvc views, , working webforms 1.0 , mvc 2.0. application setup application under default website. i've seen lots of variations same exception came down syntax errors in form helpers. seems more environmentally related. appreciated! 

this problem emerged web.config error, specifically, following 2 lines:

<add key="clientvalidationenabled" value="true" /> <add key="unobtrusivejavascriptenabled" value="true" /> 

the 2nd line broken when had invalid boolean value like:

<add key="unobtrusivejavascriptenabled" value="none" />