This happened to me in a client's WSS3 environment, but it seems to apply to 2010 as well. I had a site template created in one environment, but upon moving it to another, the Create Site operation resulted in a neat little error, complete with stack...
Custom list. Custom New/Edit/View forms. Everything works perfectly... until the latest round of updates. Now if you Bingle this error message, you'll get about twenty possible causes that run the gamut from a known bug, an unknown bug, and fixed/not...
