Just got another blue screen. Strangely, no minudump was created, only memory.dmp. Here is what whocrashed says, which is mostly the same as before...
On Fri 12/24/2010 7:26:18 PM GMT your computer crashed
crash dump file: C:\Windows\memory.dmp
This was probably caused by the following module: usbport.sys (USBPORT!USBPORT_RegisterUSBPortDriver+0x4EDE)
Bugcheck code: 0xFE (0x5, 0xFFFFFA8008F591A0, 0x80863B34, 0xFFFFFA800C4EFC50)
file path: C:\Windows\system32\drivers\usbport.sys
product: Microsoft® Windows® Operating System
company: Microsoft Corporation
description: USB 1.1 & 2.0 Port Driver
Bug check description: This indicates that an error has occurred in a Universal Serial Bus (USB) driver.
The crash took place in a standard Microsoft module. Your system configuration may be incorrect. Possibly this problem is caused by another driver on your system which cannot be identified at this time.