Try that so called ntsymbols trick - you need to make nms for your ntoskrnl; the info is on hxxp://frontline.compuware.com/nashua/kb/doc/1467.asp
Maybee this could help...

least

PS. It means you need debug symblos for your specific servicepack. If you have troubles with downloading them from MS, I can send you the file you need.

PPS. I've read that DRIVER_IRQL_NOT_LESS_OR_EQUAL means hardware collision and they advice to install newest drivers, look if one IRQ isn't shared by many devices and finally trying to disable hardware not needed (one written that modem was the guilty).