Yep. Tonight was the first that had ever happened. There were two relays loose on the driver's side (Front of the car) of the engine compartment that were loose that I had re-bolted to the frame, but no other "electrical changes" to the existing system. All work done replacing the radiator was done with the battery disconnected, so I doubt any arcing occurred.

I saw a tiny bit of steam showing up by the lower radiator hose where it enters the bottom of the radiator, but I can't seem to find it leaking anywhere else. All other lines seem to be leak free, but it still seems to overheat pretty quickly. Is it crucial for the fans to be completely flush on the radiator? With one of them, I was having a little bit of trouble getting it to seat back in completely. There may be at most 1/4 of an inch space at one end, but otherwise pretty snug.