Kevin,
I can't seem to replicate your issue. I tried with several of my own project VOB files, and purchased movie VOB files. I asked PD version as I did have some issues in an earlier version of PD. When you say importing from different players, what do you mean? Are you by chance importing the VOB files directly from the DVD's? If so, you should always move the VOB files from the DVD to your HD and then import from there.
Secondly, if you produce to a file, say mpeg2, HQ profile, with the imported VOB's on the timeline, does the produced file pop and click?
Jeff