Win2k3 assertion during machine shutdown

Hi,
While QAing our driver on a win2k3 checked build machine, I received the
following assertion twice during machine shutdown:
*** Assertion failed: Junk > 0
*** Source File: d:\srv03rtm\base\busdrv\pci\usage.c, line 58

Does anyone have an idea what the assertion is all about, and whether my
driver could cause it. (My driver is a volume upper filter).

Thanks,
Eran.