When I Press F5 on my VS2005 to debug the application, it launches the web app window but it is coming out of debug mode. When I tried to trace the Error in the EventViewer, this was the error:
Failed in Token.vb(GetToken). The token was not in memory and the identity of the authenticated IIS caller was not permitted. The session may have unexpectedly terminated. The specific error message included: Session state can only be used when enableSessionState is set to true, either in a configuration file or in the Page directive. Please also make sure that System.Web.SessionStateModule or a custom session state module is included in the \\ section in the application configuration.
I don't have any httpModules section in my config file and the sessionState mode="InProc"...
Looks like your application has a code file named Token.vb that is trying (unsuccessfully) to access data stored in session state. The session state is not made available to all requests - it depends on the type of file being served (pages do get session state, static files such as images do not). If the code in Token.vb is being executed during a request for a static file, for example, I'd expect to see the error you described.