There was a loud snap, some smoke...and my computer went dead.  Turns out YET ANOTHER power supply went dead.  I'd been PLANNING to put together a dual rail PSU but, now I need to get another anyway so I might as well get an extra beefy PSU (and what the heck, throw together a 2 rail PSU of my own).

And yes, I opened up the PSU.  There was copper/solder deposited on the PCB (ie, it was vaporized off the coil) and the fuse had also blown.  Oh well.