Well, I got my computer back a few days ago, and haven't had any problems, so it seems like they fixed it. The first thing they had to do was roll back that motherboard firmware update. They couldn't get it to boot to Windows with that installed.

The part that took them a while was that there was some problem with the processor running 64-bit applications, according to the technician. I've never heard of that, but they were able to get Intel to send out a new processor since it was still under warranty. They put in the new processor and everything seems to be working fine. I definitely wouldn't have been able to do that, so I'm glad I took it in. Thanks for all your time, though.