Resource Handler / Ext.NET initialization

Occasionally when debugging in Visual Studio I get an error on first run:

Ext.Net.InitializationScriptNotFoundException was unhandled by user code
Message=The Ext.NET initialization script was not found.
Source=Ext.Net
StackTrace:
at Ext.Net.ResourceHandler.ProcessRequest(HttpContext context) in C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs:line 137
at System.Web.HttpApplication.CallHandlerExecutionSte p.System.Web.HttpApplication.IExecutionStep.Execut e()
at System.Web.HttpApplication.ExecuteStep(IExecutionS tep step, Boolean& completedSynchronously)
InnerException:

Source file information:

Locating source for 'C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs'. Checksum: MD5 {49 82 3b c fc a6 47 72 8a a6 2 69 d b7 e1 b0}
The file 'C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs' does not exist.
Looking in script documents for 'C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs'...
Looking in the projects for 'C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs'.
The file was not found in a project.
Looking in directory 'C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\crt\src\'...
Looking in directory 'C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\atlmfc\src\mfc\'...
Looking in directory 'C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\atlmfc\src\atl\'...
Looking in directory 'C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\atlmfc\include\'...
The debug source files settings for the active solution indicate that the debugger will not ask the user to find the file: C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs.
The debugger could not locate the source file 'C:\Users\Geoffrey McGill\Documents\Visual Studio 2010\Projects\Ext.NET\v2\Ext.Net\Core\ResourceHand ler.cs'.




My resource manager settings are:

<ext:ResourceManager ID="ScriptManager1" runat="server" ScriptMode="Debug" CleanResourceUrl="true" InitScriptMode="Linked" Namespace="MYCUSTOMNAME" />