The problem appears to be with the $LOG() command, disabling it completely seems to keep the crashes away.
Crashes occured both with Mozilla 1.0 Gold, and Opera 6.04.
My firewall is Kerio Personal Firewall, version 2.1.4 (driver 3.0.0)
The actual crash is in fwdrv.sys, the error is DRIVER IRQ NOT LESS OR EQUAL.
The not completely loaded pages can't be easily reproduced, but it appears to only happen on pages that use large tables (such as this forum).