Whenever I attempt to change the format in the Output Module, After Effects freezes up on me and won't let me do anything. Quicktime is the only format that has no problem rendering out. Any reasons why this would happen?
Can't help if you're on a PC, but if you're using a Mac, then the best advice I can give is trash both the AE preferences and the Quicktime preferences. Then reboot. A repair permissions wouldn't hurt either.