Created attachment 147805 [details]
After system hangs I rebooted system and panic on mount root with Fatal double fault.
OCR of stack trace attached, but it have some OCR specific troubles.
Original screenshots available there:
I also got same problem on another i386 system with 10.0-RELEASE.
Problem occurs only after unclean shutdown.
Screen photos for two different panics also available on this link.
Problem exists ONLY on i386 systems.
Problem solves after booting amd64 kernel and after "clean" reboot.
My kernel build with gdb support, I can try to collect some additional information.
You need to increase kernel stack size. Seems it is too small on i386 to handle traverse_visitbp recursion in ZFS.
I'm complete idiot.
UPDATING/20121223 answers me about this trouble.