Ok, here's the log after a crash. Interestingly didn't get a kernel panic this time, just became unresponsive and needed a hard reset. Leading up to this, the system had only been on a few hours, no changes to it from previous (it had been on over a week with no problem, only shut it down to switch a power cable). The log is full of stuff that isn't usually there, so I'm assuming it's indicative of the problem. Some of the symptoms were a few cores spiked to 100%, and then the system ground to a halt a few minutes later.
If anyone has insights, I'd appreciate it. Thanks!
diagnostic.rtf