I was fitting a replacement DVD+RW drive to one of the machines today and when I plugged it back in, the PSU on this unit (which I've had odd experiences with before) blew.

It did so in spectacular fashion - not only did it blow, but it also tripped the UPS and the UPS blew the fuse on the plug. The UPS is toast - I'm waiting for a judgement from APC on what to do next.

Fortunately I'm prepared - I have two UPS units, and each one is capable of protecting all the equipment in the server room. By splitting it in two, I can be sure that I'm protected in the event of a failure of one of the units. Obviously I had some kind of subliminal premonition.