I initially thought a Windows update went awry, but finally got a clue when one of the workstations that was semi-functional had Panda pop up a warning that the graphics driver was infected.
I was able to get about 90% of the PCs back in order using System Restore. Some were too far gone and I ended up re-imaging them from a backup. Luckily their server was running a different AV product, so I was able to pull the images without too much hassle. In all, I had about 25 workstations back up within about an hour and a half working by myself, and that included uninstalling Panda (leaving the quarantined files in place so I could move them back later) and just using Microsoft Security Essentials until I find them another AV. I'm usually willing to give companies second chances, but Verizon has ruined it for everyone and has made me rethink that policy. Also working against Panda is the fact it took them almost 24 hours to release a cleanup tool. Granted, I'm glad they took time to test it, but the response time was just awful.