a issue about Event 11 in Event viewer, because of my filter driver.

Hello
I am developping a media card drivers, which includes a filter driver,
the filter driver hooks onto my card reader driver and pcmicia.sys. my
platform is windows XP.
when standby system, and wake up it, the event viewer will show a error
event, which's id is 11, means the cable connected to the disk drive is
invalid. but the media disk such as memory stick or SD card can be accessed.
if the filter driver do not hook onto the pcmica.sys, there is no this
error event.

Can u you give me a idea, why has the error event 11?

Thanks
BR

Leon