Adding to my last comment, I don't recall ever having the problem under XP, but I had PPro 2 for only a short time under XP and my memory isn't as good as it used to be.

"random playback problems"
have and have the tickets to prove it,
Vista is not supported tll Vista is Supported....
I would rather this bug go away in XP

I've seen this bug in XP with Cineform and PPro also. Had to restart my project or delete my cache files. Also, on occasion I have imported my project into a new project and that has helped. It is annoying. While I cannot say it is a Cineform problem directly, I can say that I have never seen this when using Premiere ntaive presets.

Peace.