A while ago, I said "Still having a hard time catching Racket or Ubuntu "in the act"... One thing that seems to happen fairly consistently is that I end up waiting a lot on the background syntax expansion. Sometimes Racket recovers. Sometimes it crashes (or perhaps Ubuntu is shutting it down -- it's trying to send error reports, but can't figure out exactly what Racket is). Since turning the expansion off, I haven't had a crash." Thanks to Neil & Robby for their hints on Linux tools. None of them found any problems pointing at Racket, but they helped me down a trail where it seems pretty certain that I have a hardware problem, specifically a bad memory chip that explains the Windows BSOD, the various random Linux failures (the common thread being high memory usage that increases the likelihood of encountering the memory errors, but never came close to memory swapping issues, I suspect that's why stopping backround expansion helps). I'll send along an update when I get a final resolution or if I find a reason directly implicating Racket. Again, thanks to the community, especially Robby & Neil. Pat