No HU's, No Clock and No Buzzer, why?
 

Ok, this weird thing happened this morning. I went out for a short trip and noticed that neither of my two HU's were working (one is the stock Pioneer HU, the other is a Sony CD HU), so thought "Ok, I'll have a look at this later tonight".
Then later in the day, I had to go out again and now not only were the HU's not working, but the clock and reminder buzzer (the one that beeps when you leave key in the ignition) were not working either. My first thought was damn, must have blowen a fuse, so I had a look at the Audio one, it was fine, then had a look at the rest, and they were all fine too.

What the hell happened and how do I go about fixing it?