I doubt your system would went panic even with sysctl knobs turned on.

(see this /sys/i386/isa/intr_machdep.c)

My box is crying just the same way suddenly and it seems even FreeBSD's mail archive keeps nothing bout it... My the most belived suspection is IDE system, for now.

(you may contact me via this email: poige 4t morning d0t ru).