I get this when plugging and unplugging a USB mouse into my laptop

usb 2-1: new low speed USB device using uhci_hcd and address 2
usb 2-1: new device found, idVendor=046d, idProduct=c016
usb 2-1: new device strings: Mfr=1, Product=2, SerialNumber=0
usb 2-1: Product: Optical USB Mouse
usb 2-1: Manufacturer: Logitech
usb 2-1: configuration #1 chosen from 1 choice
input: Logitech Optical USB Mouse as /class/input/input5
input: USB HID v1.10 Mouse [Logitech Optical USB Mouse] on usb-0000:00:1d.0-1
usb 2-1: USB disconnect, address 2
BUG: atomic counter underflow at:
 [<c01d4359>] kref_put+0x59/0xa0
 [<c018f0e8>] sysfs_hash_and_remove+0x118/0x150
 [<c02f2184>] klist_remove+0x14/0x40
 [<c0220ca2>] bus_remove_device+0x82/0xa0
 [<c021f7ab>] device_del+0xfb/0x130
 [<c024bad7>] usb_disconnect+0x97/0xe0
 [<c024c540>] hub_thread+0x210/0xbe0
 [<c012b280>] autoremove_wake_function+0x0/0x50
 [<c024c330>] hub_thread+0x0/0xbe0
 [<c012b0e5>] kthread+0xe5/0xf0
 [<c012b000>] kthread+0x0/0xf0
 [<c0100875>] kernel_thread_helper+0x5/0x10
BUG: unable to handle kernel NULL pointer dereference at virtual address 00000000
 printing eip:
c02f2cf8
*pde = 00000000
Oops: 0002 [#1]
4K_STACKS PREEMPT 
last sysfs file: /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1:1.0/bInterfaceProtocol
Modules linked in:
CPU:    0
EIP:    0060:[<c02f2cf8>]    Not tainted VLI
EFLAGS: 00010086   (2.6.18-rc1-mm2 #1) 
EIP is at wait_for_completion+0x48/0xf0
eax: dec210b4   ebx: dec210b0   ecx: 00000000   edx: 00000000
esi: dfe09ef0   edi: c0354320   ebp: dfe09f00   esp: dfe09ee4
ds: 007b   es: 007b   ss: 0068
Process khubd (pid: 106, ti=dfe09000 task=dfe0b550 task.ti=dfe09000)
Stack: 00000001 dfe0b550 c0113c70 dec210b4 dec210a0 dec210c0 dec21058 c14ed458 
       c0220ca2 dec21058 dec210c0 00000000 c021f7ab dec212a4 00000010 dec21000 
       dec21058 c024bad7 c0324e0c c031db9b dec210fc 00000002 c14ed664 00000100 
Call Trace:
 [<c0113c70>] default_wake_function+0x0/0x10
 [<c0220ca2>] bus_remove_device+0x82/0xa0
 [<c021f7ab>] device_del+0xfb/0x130
 [<c024bad7>] usb_disconnect+0x97/0xe0
 [<c024c540>] hub_thread+0x210/0xbe0
 [<c012b280>] autoremove_wake_function+0x0/0x50
 [<c024c330>] hub_thread+0x0/0xbe0
 [<c012b0e5>] kthread+0xe5/0xf0
 [<c012b000>] kthread+0x0/0xf0
 [<c0100875>] kernel_thread_helper+0x5/0x10
Code: 00 00 89 e0 25 00 f0 ff ff 8b 00 8d 75 f0 c7 45 ec 70 3c 11 c0 c7 45 e4 01 00 00 00 89 45 e8 8d 43 04 8b 50 04 89 45 f0 89 70 04 <89> 32 89 55 f4 8d 76 00 89 e0 25 00 f0 ff ff 8b 10 c7 02 02 00 
EIP: [<c02f2cf8>] wait_for_completion+0x48/0xf0 SS:ESP 0068:dfe09ee4
 <6>note: khubd[106] exited with preempt_count 1