panic attaching usb

Hello,

I just mounted my external USB drive and received the following panic. 
This machine is running amd64 8.0-CURRENT from  05/28/2008.  If any
other info is required I'll be more than happy to provide it.

db> s

Fatal trap 12: page fault while in kernel mode
cpuid = 1; apic id = 01
fault virtual address   = 0x18
fault code              = supervisor read data, page not present
instruction pointer     = 0x8:0xffffffff80248450
stack pointer           = 0x10:0xffffffff808d0770
frame pointer           = 0x10:0xffffffff808d0780
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags        = trace trap, interrupt enabled, resume, IOPL =
0
current process         = 17 (usb1)
[thread pid 17 tid 100029 ]
Stopped at      _mtx_assert+0x60:       movq    0x18(%rdi),%rax
db>bt
Tracing pid 17 tid 100029 td 0xffffff0001170000
_mtx_assert() at _mtx_assert+0x60
xpt_release_ccb() at xpt_release_ccb+0x49
probedone() at probedone+0x29a
camisr_runqueue() at camisr_runqueue+0x1a7
xpt_bus_deregister() at xpt_bus_deregister+0x185
umass_cam_detach_sim() at umass_cam_detach_sim+0x1f
umass_detach() at umass_detach+0xcf
device_detach() at device_detach+0xa4
usb_disconnect_port() at usb_disconnect_port+0x8b
uhub_explore() at uhub_explore+0x10d
usb_discover() at usb_discover+0x38
usb_event_thread() at usb_event_thread+0x7c
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffffff808d0d30, rbp = 0 ---
db>show alllocks
Process 924 (ntpd) thread 0xffffff00013a56c0 (100091)
exclusive sleep mutex sigacts r = 0 (0xffffff000126eca8) locked _at_
/usr/src/sys/k
ern/subr_trap.c:223
exclusive sleep mutex process lock r = 0 (0xffffff000139d0f8) locked _at_
/usr/src/
sys/kern/subr_trap.c:222
Process 17 (usb1) thread 0xffffff0001170000 (100029)
exclusive sleep mutex Giant r = 0 (0xffffffff80585540) locked _at_
/usr/src/sys/dev
/usb/uhub.c:639
db>show thread 100029
Thread 100029 at 0xffffff0001170000:
 proc (pid 17): 0xffffff000116a860
 name: usb1
 stack: 0xffffffff808cd000-0xffffffff808d0fff
 flags: 0x10005  pflags: 0x200000
 state: RUNNING (CPU 1)
 priority: 24
db>tr 100029
Tracing pid 17 tid 100029 td 0xffffff0001170000
_mtx_assert() at _mtx_assert+0x60
xpt_release_ccb() at xpt_release_ccb+0x49
probedone() at probedone+0x29a
camisr_runqueue() at camisr_runqueue+0x1a7
xpt_bus_deregister() at xpt_bus_deregister+0x185
umass_cam_detach_sim() at umass_cam_detach_sim+0x1f
umass_detach() at umass_detach+0xcf
device_detach() at device_detach+0xa4
usb_disconnect_port() at usb_disconnect_port+0x8b
uhub_explore() at uhub_explore+0x10d
usb_discover() at usb_discover+0x38
usb_event_thread() at usb_event_thread+0x7c
fork_exit() at fork_exit+0x12a
fork_trampoline() at fork_trampoline+0xe
--- trap 0, rip = 0, rsp = 0xffffffff808d0d30, rbp = 0 ---
db>