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?)