::update::
It's not a case of a bad AGP slot, as other cards worked fine. However, they also didn't require 12V connections, which means it sounds like I have a classic case of "bad PSU." Any thoughts?
Thinking I was long overdue to get ready for the next-gen games, I decided to blow a wad of cash and spring for a new rig. $1200 later, the fun's just begun. I went with the Leadtek 6800 GT in conjunction with a DFI Lanparty UT NF3 250GB mobo, a Clawhammer 3200+, and Thermaltake's 480W Silent...