Screen Corruption and System Hang when entering text

[HenryHu]

When I was doing text input using SCIM input method, the screen corrupts, and the music stop playing. This has happened several times.
If I switch to a console as soon as possible, I would got the console after several seconds, and after switching back to the X, everything go on after some seconds.
But if I continue entering, the system would lag several times, and then stop responding. There are NVRM messages when this happend. Log attached.

PS. As I remember, I was doing text input in firefox when this happened...

[HenryHu]

Finally I've got a kernel dump.

Unread portion of the kernel message buffer:
panic: vm_fault: fault on nofault entry, addr: d97e8000

(kgdb) where
#0 doadump () at pcpu.h:196
#1 0xc05e36d7 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:418
#2 0xc05e39d3 in panic (fmt=Variable "fmt" is not available.
) at /usr/src/sys/kern/kern_shutdown.c:572
#3 0xc07a0508 in vm_fault (map=0xc1871000, vaddr=3648946176, fault_type=1 '\001', fault_flags=0) at /usr/src/sys/vm/vm_fault.c:275
#4 0xc081832e in trap_pfault (frame=0xe849da2c, usermode=0, eva=3648946196) at /usr/src/sys/i386/i386/trap.c:841
#5 0xc0818d22 in trap (frame=0xe849da2c) at /usr/src/sys/i386/i386/trap.c:530
#6 0xc07fec1b in calltrap () at /usr/src/sys/i386/i386/exception.s:159
#7 0xc0c304ae in _nv008339rm () from /boot/modules/nvidia.ko
Previous frame inner to this frame (corrupt stack?)