I get an error message when I try to select the vanishing point filter that the operation could not be completed. I tried the vanishing point filter on two different PSD files and both times I got the same message so the error is not specific to any one file.
I believe the vanishing point filter somehow remembers an error in afile once you do something in it that the vanishing point filter doesn't like. (I had already run the filter on the two effected files several times before.) Using the save as command and changing the names of the files didn't correct the problem. It was only when I copied and pasted the layers of the files to new files that the problem was fixed. I think i this is is another CS3 photoshop bug. I found on the Adobe Labs forum that other users were having the same issue.