Just tried using Premiere CS5.5. I opened a CS5 project, but when I try to play any of the videos, either in the Source Monitor or Program monitor, the playback stops after a fraction of a second. It doesn't matter what point in what video I'm at. On the other had, scrubbing through the videos is no problem.
Does anyone have an idea what could be going on here? Needless to say, it's impossible to do any work within Premiere under these circumstances.