computer freezes on PT launch!

[tomcat]

this is a new one on me. today, when i launch protools (4.3.1, os 8.1) everything seems fine until protools is actualy completely launched, no session open, at which point the computer (ptp 225, g3 250 newer) freezes and must be restarted. i have chucked the prefs (pt, dae, digisetup) and am trying other stuff right now, but nothing has changed (no new extensions) in the system since yesterday's successful session. is this ringing a bell with anyone???

thanks

[tomcat]

ok it works now. i don't know...could be a number of things. turned off the hui, took it out of the adb chain, dumped a few nonessential extensions, trashed the prefs again, blah, blah,blah, have a good night.
t