Got this wacky error when trying to complete a build.
Delete VSWebCache! This answers about 80% of the issues for opening ASP.NET.
The VSWebCache folder is created automatically by Visual Studio when you open/create a web project and can be found in <root>\Documents and Settings\<user>\VSWebCache\<machinename>.
Visual Studio .NET cannot create or open the application. The likeliest problem is that required components are not installed on the local web server. Run Visual Studio .NET setup and add the Web Development component.