I have had an even more severe problem with Apple AU effects. Everytime I add one on an audio track, or sometimes only when I play a track with one of the effects, Metro quits and I get the standard OS X bug report message.
I am running Metro 6.2.2 G4 on an iMac G5 in OS 10.3.9
The problems begun after I installed a new AU-plugin. I don't know if it was a coincidence. I have tried to delete the new plugin and repair permissions. I have also restarted the computer (several times).