It definitely helped to re-associate the .vb files but now now that I have moved them to the app_code folder, the app no longer sees them and I get a page not found.
I am passing the report as http://localhost/MyApp/MyRpt.rpx?OutputFormat=pdf&stDate=11/1/2005&endDate=11/30/2005 and it is giving me the above error. It worked with VS2k3. TIA