I turned off my computer, unplugged everything, opened it up and took out the graphics card and got the air blower ready. I then BLEW all the dust out of my computer with the air compressor (my Kirby vacuum cleaner- with the proper attachment it comes a damned good but DAMNED LOUD air compressor :) ).
Then I put the graphics card back in, closed the case back up, plugged it back in and turned it on.
And was HORRIFIED when it told me I needed to enter SETUP to recover my BIOS. I tried, but the video only showed 1/4 of the screen with no movement- had to turn it all off.
Spent the next HOUR fighting with my computer. It would start to load, then blue screen. Would start to load, then give me a device missing error. Finally, it told me to enter SETUP again and I did so- looked at the settings, left. It blue screened. Then it loaded further, device missing errored. Loaded FURTHER, blue screen and NOW it's loaded and it seems to be stable...
I do not know why it had such problems and I can only hope it will continue to start when I turn things on in the morning :| If I go suddenly dark, now you know WHY.