just a guess, maybe one of your plugins has reverted to demo mode for some reason ?

It's happened to few people I know including myself and nobody seems to know why.

i didn't have any plugins on that track at all. It didn't happen during tracking, just on playback. I talked with Digi, they seemed to think it was a hard disk issue. To me, that seems to make sense. I did another session on another hard drive and didn't have any issues. I just don't know whether to reformat the drive or to just ditch it. I can't afford to sacrifice blowing ears out and screwed up audio?!

What plugs did you have running in the session, and where was the system usage meter? I ask because I had a similar problem occur with playback of a fairly big session, a few RTAS GRM Tools plugs and... ALTIVERB. That one must have pushed it over the edge. I notice when the meter is in the yellow, Altiverb freaks out with noise. Everything had been working fine just an hour before, then all of a sudden...