Hope this helps anyone with a QT7.3 problem. It appears to me that there was a new player loaded with the 7.3 update and somehow that player does not connect with the MBox when it is launched with a file, rather than by itself.

The sequence that DOES work is boot, wait for core audio to load, open QTPlayer. So far the sequence that does NOT Work is boot, wait for core audio to load, double-click aiff file to play with QTPlayer: File plays but no audio out through MBox. Its just the initial startup that seems to be the problem.

Once QuickTime Player is open, double-clicking a file opens and plays. However, opening QuickTime Player and then opening an audio file is fine. It seems that double clicking a file to open and play using QuickTime Player does not work. Question: Q: Quicktime 7.3.1 how do i uninstall this version and get the previous one i had back i run pro tools on panther, now it won't even load. The funny thing is this: After playing with system preferences and quiting and restarting core audio, it started working!!! Good. The problem seems to be playing audio files through QuickTime Player. System was fine, I booted and got software update with a new ITunes (and QT7.3) Installed No Audio Out. The computer in question is a G4 running up to date Tiger and now Quicktime 7.3. Rating:0of 5Rate It (0votes) Tested:Free from spyware, adware and viruses. I just upgraded to QuickTime 7.3 and experienced problems playing audio out through a MBox.

Quicktime download 7.3.1