In trying to get my Rails 2.3.5 application up and running, I got rbx built at d7274f3 to crash on OS 10.6.2 on a Core 2 Duo. I managed to get it to crash with JIT turned off inside gdb once, and here is what I got out of it. Not a whole lot to go on, I know, but it's the best I can get now that the heisenbug has disappeared. It did fail with JIT turned off and with it turned on.
Unable to repro. We've fixed a number of segfault bugs, so this is probably fixed.