playback crash

PowerBookG4 10.3.9 512MB RAM, 50GB Hard Drive, 30GB available, FCPHD 4.5
Playback of internally generated Bars and Tone as well as DV media captured from Sony BSP UVW-1800 through Sony DVMC-DA2 through FW400 port to Hard Drive CRASH FCP.
I've already trashed prefs and created a new user. FCP worked OK for a while, then same crash.
QT files generated by FCP during capture play back fine using QT7.
No norton on drive, no virex either.

THANKS!!!

Sounds like the system needs maintenace, or there was some kind of problem with the install.

Did you repair permissions yet? Run the Disk utility and Disk warrior. If none of this helps, I'd reinstall the lot.