I've tried MMPlayer, Real Player, and Pocket Tunes on my 650 as well as tested with over 20 mp3s and I still get the same behavior. During mp3 playback, I'll get 1 second of this odd, ripple like static every 10-30 seconds (kind of hard to describe), no precise pattern and its was really starting to bug me that I could not figure this out (was starting to fear it was a Treo bug). After some analysis, finally figured out the problem. The problem only occurs during mp3 playback if I go into the camera app AND take a picture. This single camera click sound somehow introduces multiple instances of this occasional static into the mp3 playback for the current track and any subsequent tracks played back. The only way I found to get rid of it was to do a soft reset. Thought I'd post this in case anyone else was having a similar issue.