Twice today, I saw my ath0 interface drop carrier.  I typed

	ifconfig ath0 down

to see if bringing it back up would repair the link.  Both times, the 
machine rebooted immediately, with no visible messages, panics, etc.
I'm running 3.99.11 from 8 November; ironically, at the time of one 
crash I was building a new kernel because I saw the report about 
bringing in the newer 802.11 code.

		--Steven M. Bellovin, http://www.cs.columbia.edu/~smb