Logic Pro 8 Logic 8 session crashing numerous ways

Made To Feel

I'm scoring a 4 minute video with numerous short cues (17 instrument trks, 4 audio trks) and starting yesterday (about 2/3rds of the way into the project) it began crashing in numerous spectacular ways.

* dumping my Kontakt 5 multis (shows an empty rack when I open the file)
* occasionally dumping my BFD2 kit (showing empty kit)
* giving me the white screen of death on screen or another, blinks when I click

It works fine for awhile, but then some little straw will break the camel's back. It appears to be teetering near the brink of some kind of overload but I can't figure out which.

I'm working on a 6-core 3.33 gHz MacPro with 24G of RAM, running my sessions off a 1TB Seagate FreeAgent GoFlex & samples from a 1TB WD MyBook. Shouldn't this setup be powerful/fast enough to handle this kind of thing? (My interface is a ~4-yo. mBox2 Pro.)

I've been watching the CPU/HD meters and don't seem to be getting any problems. Ironically, freezing tracks causes *more* spikes in my disk I/O.

Any suggestions mucho appreciated.