I upgraded from 2.3.5.4 to 2.3.6.7 and migrated to dotnet 4.0.  I backed up my site and my database, upgraded the server to dotnet 4.0.  Changed the IIS settings to they would be 4.0 as well.  Overwrote the files with the files in mojoportal-2-3-6-7-mssql-net40-deploymentfiles.zip and ran the setup/default.aspx page.  I didn't get any errors during the upgrade but now I am getting the error below when I try to load the page.  Any ideas?

Server Error in '/' Application.
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Value cannot be null.
Parameter name: format
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.ArgumentNullException: Value cannot be null.
Parameter name: format

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. 

Stack Trace:

[ArgumentNullException: Value cannot be null.
Parameter name: format]
   System.String.Format(String format, Object arg0) +9607838
   mojoPortal.Web.UI.WelcomeMessage.DoRender(HtmlTextWriter writer) +295
   mojoPortal.Web.UI.WelcomeMessage.Render(HtmlTextWriter writer) +94
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +65
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +270
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +26
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208
   System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter writer) +177
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +31
   System.Web.UI.HtmlControls.HtmlForm.Render(HtmlTextWriter output) +311
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +65
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +270
   System.Web.UI.HtmlControls.HtmlForm.RenderControl(HtmlTextWriter writer) +53
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +9
   System.Web.UI.Control.Render(HtmlTextWriter writer) +10
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +65
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +270
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +26
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +208
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +9
   mojoPortal.Web.mojoBasePage.Render(HtmlTextWriter writer) +49
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +65
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +270
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +26
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +9711

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Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1

I don't see that file in the directory you mentioned in the zip file mojoportal-2-3-6-7-mssql-net40-deploymentfiles.zip.

The site is missing a lot of images now and the content doesn't line up.  http://www.motormastersnj.com/

Thanks guys.  I reset all the skins to default and that fixed the issue.  I think I'm going to leave them as default from now on.  Everything else looks good.