I'm using the trial of Premiere Pro CS5 on a 2x2.8 Ghz Quad-Core Mac Pro with 6 GB RAM. I'm currently trying to put together a video with footage from my 5D. Even after I render the work area, the playback will randomly stop several seconds after I starts it.
Also, for the audio problem, it doesn't seem to matter what kind of footage I'm editing. The audio track I'm working on will cut out randomly as the video is playing and will sometimes loop.