Same problem here.
Dual 3GHz 10.5.6 updated to the max
permission repaired (although it found nothing)
more details about the problem here is that waveform display slows down before crashing. seems like RAM problem but we work on 2 suites here on the same sequences but only one of them suffers from the crashes.
The network is connected but all media is local.
Another thing is that from time to time, the render manager looses all connections to the renders (have do delete them manually)
The FCP won’t Force quit on the Finder level.
any more suggestions?