I deployed a sample ASP .NET 2.0 app in to the _layouts directory of a WSS v 3 setup. This app was not precompiled.
When the app runs, executing code that accesses the SP object model gave me the error "Unable to Validate Data".
I can think of any reasoning behind that error.
But after resetting IIS, all was fine.
Note to Self: Recycle the Application pool after each deployment.
Technorati : 2007, Sharepoint, Wss, v3
Cross-posted from tariqayad.com