I have had nothing but great experiences with JKII in general, and never a *single* crash - either on JKII or Jedi Academy - using either my older TiBook 1GHz or my current Aluminum Powerbook 1.25 15".
What hardware do you have? I assume you're running OS X? What version? Have you done the usual defrag/virus check/repair permissions deals?
What other Q3-based games (e.g. Elite Force 1&2, MoHAA, RtCW, SoFII etc) are you running successfully?
I'll help as best I can,
Dopelar effect (n.) The tendency of stupid ideas to seem smarter when they come at you rapidly.