panic 01/25/04 kernel in uhci uplcom

I got a panic on a recent kernel:

FreeBSD server.mcneil.com 6.0-CURRENT FreeBSD 6.0-CURRENT #2: Fri Jan  7
18:21:53 PST 2005     root_at_server.mcneil.com:/usr/obj/usr/src/sys/AMD64
amd64

Jan 25 23:50:39 server syslogd: kernel boot file
is /boot/kernel.old/kernel
Jan 25 23:50:39 server kernel: panic: uhci_abort_xfer: not in process
context
Jan 25 23:50:39 server kernel: Uptime: 1m39s
Jan 25 23:50:39 server kernel: interrupt                   total
Jan 25 23:50:39 server kernel: irq1: atkbd0                           2
Jan 25 23:50:39 server kernel: irq0: clk                         323813
Jan 25 23:50:39 server kernel: irq4: sio0                             5
Jan 25 23:50:39 server kernel: irq8: rtc                          20738
Jan 25 23:50:39 server kernel: irq14: ata0                          722
Jan 25 23:50:39 server kernel: irq15: ata1                          186
Jan 25 23:50:39 server kernel: irq16: re0                            62
Jan 25 23:50:39 server kernel: irq17: fwohci0                         1
Jan 25 23:50:39 server kernel: irq19: dc0                             2
Jan 25 23:50:39 server kernel: irq20: atapci0                      6006
Jan 25 23:50:39 server kernel: irq21: uhci0 uhci1+                  136
Jan 25 23:50:39 server kernel: Total                      351673
Jan 25 23:50:39 server kernel: KDB: stack backtrace:
Jan 25 23:50:39 server kernel: hardclock() at hardclock+0x1eb
Jan 25 23:50:39 server kernel: intr_execute_handlers() at
intr_execute_handlers+0x102
Jan 25 23:50:39 server kernel: lapic_handle_intr() at lapic_handle_intr
+0x21
Jan 25 23:50:39 server kernel: Xapic_isr1() at Xapic_isr1+0x7d
Jan 25 23:50:39 server kernel: --- interrupt, rip = 0xffffffff802eb1e1,
rsp = 0xffffffffb19187e0, rbp = 0xffffffffb1918810 ---
Jan 25 23:50:39 server kernel: cv_wait() at cv_wait+0x1
Jan 25 23:50:39 server kernel: ata_queue_request() at ata_queue_request
+0x1e8
Jan 25 23:50:39 server kernel: ata_controlcmd() at ata_controlcmd+0x8b
Jan 25 23:50:39 server kernel: ata_shutdown() at ata_shutdown+0xb8
Jan 25 23:50:39 server kernel: boot() at boot+0x25c
Jan 25 23:50:39 server kernel: panic() at panic+0x167
Jan 25 23:50:39 server kernel: uhci_abort_xfer() at uhci_abort_xfer+0x68
Jan 25 23:50:39 server kernel: usbd_abort_pipe() at usbd_abort_pipe+0x27
Jan 25 23:50:39 server kernel: ucomstopread() at ucomstopread+0x27
Jan 25 23:50:39 server kernel: ucomstop() at ucomstop+0x2f
Jan 25 23:50:39 server kernel: ttyflush() at ttyflush+0x34
Jan 25 23:50:39 server kernel: ttymodem() at ttymodem+0x9e
Jan 25 23:50:39 server kernel: ucom_status_change() at
ucom_status_change+0x93
Jan 25 23:50:39 server kernel: uplcom_intr() at uplcom_intr+0x94
Jan 25 23:50:39 server kernel: usb_transfer_complete() at
usb_transfer_complete+0x201
Jan 25 23:50:39 server kernel: uhci_softintr() at uhci_softintr+0x100
Jan 25 23:50:39 server kernel: uhci_intr1() at uhci_intr1+0xd5
Jan 25 23:50:39 server kernel: ithread_loop() at ithread_loop+0xd3
Jan 25 23:50:39 server kernel: fork_exit() at fork_exit+0x8f
Jan 25 23:50:39 server kernel: fork_trampoline() at fork_trampoline+0xe
Jan 25 23:50:39 server kernel: --- trap 0, rip = 0, rsp =
0xffffffffb1918d00, rbp = 0 ---