No SLI option, second GPU not detected after driver update

From what I understand, this is a somewhat common problem, but I thought I'd start a new thread rather than try to dig up some old one about it.

Background on my issue:
Windows 7 Home Premium 64bit
Rebuilt my PC with a Gigabyte Z68XP-UD4 board and i5 2500k CPU.
Everything installed and ran perfectly. Zero hardware or software issues.
I've been running two GTX 465's in SLI configuration. They ran fine right after I first installed their drivers. SLI worked perfectly.
Everything was going well. I was benchmarking Crysis, playing Skyrim, all that good stuff. Then, I booted my PC this morning, and Windows was automatically updating drivers. I checked which ones they were, and among them were PCI bridge, PCI to PCI connector, etc. Since the update, I no longer have SLI. In fact, my second GTX 465 doesn't even show up in the Device Manager. In the Nvidia control panel, there is no option for SLI, it just show "Set PhysX Configuration."
I'm pretty sure there's a quick fix for this, but nothing I'm doing seems to work. Anyone know how to resolve this?