I have read almost everything in this thread, searched up and down around the websearch. Read like ten different threads each for my graphics card ( which I thought was dead: 6800GT), and a ATI 5700, ( that I know worked, cus already have tested it on my other computer).
Okey, now I'm really on to something, since I live of repairing computer, etc. I was not going to throw my motherboard away, it has worked for not long ago, and I now just was about to sell my computer and suddenly lately there has been this blackscreen at startup (No Signal).
What's important to understand is that even with a small coating on the motherboard there still can be dust and other small particles which can lead to mailfunctioning, or bugging, in the worse case blackscreen, etc.
So I unplugged the whole computer power, on the mainboard and at the back of the PSU (power supply), and then got to work! :) I removed all of my compontents, then pulled out a (don't know what it's called: what we use to cleanse our ears with)and a flashlight,(for me it goes with a bluish britght light which is very useful when looking at small components/areas in the computer), and then removed all dust particles ( in the computer cabinet/mainboard/graphic card/RAM, etc.,the all which I could see with my eyes. Then againg checked the cards connectors, cleaned them too, so no fat, dustparticles, etc is covering the connectors to the motherboard ( when I put the cards back on the motherboard). Also it is important to check the pins of RAM, Graphics, (AGP, PCI, ETC ports) for dust, if so, clean it away ( ear cleaner or some small plastic which cannot harm the card).
So everything looks fine, as it allways have, yet I cannot understand why the blackscreen occur, and THEN SUDDENLY, when I look at a deeper level down on the back of the cpu(processor)pins, there up in the corner a pin is bent down. So now I hope the problem is solved, (as a specialist in perfectioness I will begin trying to get the pin standing up again, without hurting/damaging the pin.) Wish me luck guys, and for all of you which do not have their problem solved, I think its time to bring out the flashlight, go further and deeper into the mainbord and other hardware for searching if there is some kind of "bug" ( anything that should not be at that place at that time, should be removed :) ) and then it's time for putting the hardware back together, and remeber folks! Keep your fingers away from the metal connectors at the back/end of your cards when putting them in. Also it is preferred to take a look in the manual of the specific mainboard and such for a deeper understanding of the product and it's way of functioning! And now it is just up to the further luck to get this machine up and running, if not I probably gonna get a new CPU(The Central Processor Unit/processor).
<3 from smuuD :)