All of them have in common the notice of some process having

 "exited with preempt_count 1"

and all of them happened within three hours -- this is the first time
that a mainline kernel has been behaving so consistently unstable for
me, in fact.

The machine is a P4 Xeon 2.8GHz running Debian GNU/Linux (sarge) and
here are the lspci and lsusb -vvv output and the Kernel configuration
file: