panic after removing usb flash drive

umass0: LEXAR MEDIA JUMPDRIVE2, rev 2.00/1.25, addr 2
umass0: at uhub4 port 6 (addr 2) disconnected
panic: vm_fault: fault on nofault entry, addr: deadc000

kernel:

FreeBSD 7.0-CURRENT #2: Mon Aug 29 00:39:21 UTC 2005

problem:

kernel panics when usb flash drive is removed

backtrace:

#0  doadump () at pcpu.h:165
#1  0xc068610e in boot (howto=260)
at /usr/src/sys/kern/kern_shutdown.c:397
#2  0xc0685b92 in panic (
    fmt=0xc090e46c "vm_fault: fault on nofault entry, addr: %lx")
    at /usr/src/sys/kern/kern_shutdown.c:553
#3  0xc0812de1 in vm_fault (map=0xc1060000, vaddr=3735928832,
    fault_type=2 '\002', fault_flags=0)
at /usr/src/sys/vm/vm_fault.c:884
#4  0xc0888807 in trap_pfault (frame=0xe6a06bf0, usermode=0,
eva=3735929110)
    at /usr/src/sys/i386/i386/trap.c:741
#5  0xc0888d04 in trap (frame=
      {tf_fs = 8, tf_es = -1063649240, tf_ds = 40, tf_edi = -993875968,
tf_esi = -1014223872, tf_ebp = -425694000, tf_isp = -425694180, tf_ebx =
-1063640044, tf_edx = -993875900, tf_ecx = 0, tf_eax = -559038242,
tf_trapno = 12, tf_err = 2, tf_eip = -1069194040, tf_cs = 32, tf_eflags
= 66050, tf_esp = -1063640032, tf_ss = 0})
at /usr/src/sys/i386/i386/trap.c:442
#6  0xc08745ba in calltrap () at /usr/src/sys/i386/i386/exception.s:139
#7  0x00000008 in ?? ()
#8  0xc09a0028 in atdma_acpi_driver_mod ()
#9  0x00000028 in ?? ()
#10 0xc4c2a800 in ?? ()
#11 0xc38c2c00 in ?? ()
#12 0xe6a06cd0 in ?? ()
#13 0xe6a06c1c in ?? ()
---Type <return> to continue, or q <return> to quit---
#14 0xc09a2414 in xsoftc ()
#15 0xc4c2a844 in ?? ()
#16 0x00000000 in ?? ()
#17 0xdeadc0de in ?? ()
#18 0x0000000c in ?? ()
#19 0x00000002 in ?? ()
#20 0xc04564c8 in camisr (V_queue=0xc09a2414)
    at /usr/src/sys/cam/cam_xpt.c:7066
#21 0xc066f84e in ithread_loop (arg=0xc356fa80)
    at /usr/src/sys/kern/kern_intr.c:545
#22 0xc066e808 in fork_exit (callout=0xc066f665 <ithread_loop>, arg=0x0,
    frame=0x0) at /usr/src/sys/kern/kern_fork.c:789
#23 0xc087461c in fork_trampoline ()
at /usr/src/sys/i386/i386/exception.s:208