I have had this problem too for the last 5-6 months. Media 100 knows about it but their only solution so far is to move the audio to a different drive. Try a drive not on your raid (firewire or internal). This problem just appeared one day and I don’t know why nor can I get back to proper exports. I temporarly installed QuickTime 7 and the exporting was fixed but cleaner doesn’t work any more. I am going to return to QT6.5 and see if I still have the problem. The problem is intermitant so only some exports fail, however the ones that do only rarely work with multiple attempts.
Good luck,
Neal