I have a site that I've inherited that I'm upgrading from 4.8.4 to 6.2.2.  I've reached the 5.4.4 milestone and everything seems to be running fine except for a sub site that is written in .Net 4.0.  The sub site fails because of the following that was added to the parent web.cong during the upgrade to 5.4.4.

  <system.codedom>
    <compilers>
      <compiler language="vb;vbs;visualbasic;vbscript" type="Microsoft.VisualBasic.VBCodeProvider, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" extension=".vb" warningLevel="4">
        <providerOption name="CompilerVersion" value="v3.5" />
        <providerOption name="OptionInfer" value="true" />
        <providerOption name="WarnAsError" value="false" />
      </compiler>
      <compiler language="c#;cs;csharp" extension=".cs" type="Microsoft.CSharp.CSharpCodeProvider,System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" warningLevel="4">
        <providerOption name="CompilerVersion" value="v3.5" />
        <providerOption name="WarnAsError" value="false" />
      </compiler>
    </compilers>
  </system.codedom>

I wrapped the above information with the following tags:
  <location path="." inheritInChildApplications="false"> 
  </location>

When I do this, the main site returns an error after login.  This is the error that shows in Event Viewer:
Event Type: Warning
Event Source: ASP.NET 2.0.50727.0
Event Category: Web Event
Event ID: 1309
Date:  8/16/2012
Time:  10:54:45 AM
User:  N/A
Computer: TNEMCKEE1
Description:
Event code: 3005
Event message: An unhandled exception has occurred.
Event time: 8/16/2012 10:54:45 AM
Event time (UTC): 8/16/2012 2:54:45 PM
Event ID: 96acbaf6d51048d1846fcfffb5cd8e82
Event sequence: 37
Event occurrence: 3
Event detail code: 0
 
Application information:
    Application domain: /LM/W3SVC/1893286637/Root-3-129896002027162798
    Trust level: Full
    Application Virtual Path: /
    Application Path: C:\Webs\emckee2\
    Machine name: TNEMCKEE1
 
Process information:
    Process ID: 6136
    Process name: w3wp.exe
    Account name: NT AUTHORITY\NETWORK SERVICE
 
Exception information:
    Exception type: NullReferenceException
    Exception message: Object reference not set to an instance of an object.
 
Request information:
    Request URL: http://emckeet/Default.aspx?tabid=53&returnurl=An unhandled exception has occurred.fDefault.aspx
    Request path: /Default.aspx
    User host address: 10.15.100.34
    User: 
    Is authenticated: False
    Authentication Type: 
    Thread account name: NT AUTHORITY\NETWORK SERVICE
 
Thread information:
    Thread ID: 18
    Thread account name: NT AUTHORITY\NETWORK SERVICE
    Is impersonating: False
    Stack trace:    at DotNetNuke.Common.Utilities.XmlUtils.GetAttributeValueAsInteger(XPathNavigator nav, String AttributeName, Int32 DefaultValue)
   at DotNetNuke.Common.Utilities.Config.GetPersistentCookieTimeout()
   at DotNetNuke.Entities.Users.UserController.UserLogin(Int32 portalId, UserInfo user, String PortalName, String IP, Boolean CreatePersistentCookie)
   at DotNetNuke.Modules.Admin.Authentication.Login.ValidateUser(UserInfo objUser, Boolean ignoreExpiring)
   at DotNetNuke.Modules.Admin.Authentication.Login.UserAuthenticated(Object sender, UserAuthenticatedEventArgs e)
   at DotNetNuke.Services.Authentication.AuthenticationLoginBase.OnUserAuthenticated(UserAuthenticatedEventArgs ea)
   at DotNetNuke.Modules.Admin.Authentication.Login.cmdLogin_Click(Object sender, EventArgs e)
   at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
   at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

 
If I remove the location tags everthing runs fine except for the one sub site and it generates the following error.
Server Error in '/EventCalendar' Application.
--------------------------------------------------------------------------------

The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework. To compile this Web application for version 3.5 or earlier of the .NET Framework, remove the 'targetFramework' attribute from the <compilation> element of the Web.config file.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Configuration.Configurati sException: The value for the 'compilerVersion' attribute in the provider options must be 'v4.0' or later if you are compiling for version 4.0 or later of the .NET Framework. To compile this Web application for version 3.5 or earlier of the .NET Framework, remove the 'targetFramework' attribute from the <compilation> element of the Web.config file.

If I try to use the <clear/> tag in the sub sites web.config it squaks about unknown tag.

Any ideas?