Unexplained Keyboard/Mouse failure

This is odd... Late last night I'm running a game that I've played many years, and all of a sudden the screen goes dead, the sound stops going to my headphones, and no power is going to my keyboard or mouse:o
I then try the usual Alt-Ctrl-Del routine, but this just won't come up - it's as though the whole system has crashed, although the PSU is obviously still working, otherwise it wouldn't be on at all... I am forced in the end to shut the machine down with the standby on/off switch, something you should never do, but I had no choice.
I then switched it back on, the BIOS kicked-in, etc, and then I get the standard 'your keyboard and mouse have a problem' audio message (so at least the speakers were working), and indeed, no power was going to the keyboard or mouse.
I then repeated the same off/on routine about four or five successive times, but again I got this warning. Well, I just didn't know what to do, and in the end was 'this far' from disconecting the machine from all the leads, and taking it to my PC supplier the next morning (today), but I didn't really want to do this... In the end, out of disperation, I once again switched the machine off, and then permenantly disconnected it from the power-supply via the main on/off switch at the back - I then re-engaged the power-supply after a few seconds, and switched the PC back on via the standby switch, and this time it booted-up normally, and power was going to the kboard/mouse.
Anyway, the thing is, has anyone experienced anything like this? To me, it's as though the USB ports just temporarily packed-up, which is why no power was going to the keyboard and mouse. I have never known anything like this.

 

Many thanks phunksta,

Oddly enough, I did dust down the cpu heatsink that was covered in dust and other areas just prior to re-engaging the main on/off switch, so maybe it was a short. Scary. Just wondering what would have caused a short. But thanks for putting my mind at rest, all has been ok since...;)

 

It could have been a fleck of metal, but problem is, that I have one of these so-called stealth cubes, so it's very cramped and impossible to see what's going where. Anyway, I've since invested in an aerosole cleaning kit and it works well, which is good, because my GF doesn't like it when I use her makeup brush