Panic on -current

[walt <wa1ter@xxxxxxxxxxxxx>]

I updated world/kernel this morning and all seemed good until
I exited from my gnome X session.  Here is what kgdb says:

(kgdb) bt
#0  lwkt_switch () at thread2.h:177
#1  0xc02e2384 in trap (frame=Error accessing memory address 0x8: Bad address.
) at /usr/src/sys/i386/i386/trap.c:349
Previous frame inner to this frame (corrupt stack?)