The above error occurred after a clean install of Windows, Visual Studio, etc. While I was able to load the Web application(s) via Visual Studio 2008's debugging process (using it's "temporary server"), I could not access the application directly (through the default port) outside of VS. In other words http://localhost/AppName/default.aspx failed to load, and instead I received the above error.
This is a permissions issue.
Grant the Network Service user account Full Control access to the C:\Windows\Temp directory.