Problems with POST and other computer related problems

Not sure where I should post this. I'll give as much info as i can find on my build.

PSU is 680 watts
graphics card is a Galaxy GTS 250
2gb of ram
dual core 1.6ghz cpu
motherboard is a 945gtc-m3


it was originally an old emachines build but i've just bought new stuff for it over time to due until i can get the money up to build my own. I know quite a bit about computers, but it seems this problem here went over my head. I'm currently on the computer right now, but who knows when it's gonna mess up again.

Here's the run down on it.

Every now and then, when the computer first starts (i mean literally, first starts after its been off a while), i'll get an error code. its repeating 1 long beep and 2 short beeps (Phoenix Award BIOS). It leans to my graphics card being either faulty or not seated properly. Well, I've reseated it many times. Strange part is, it'll only give that error on the first shot on turning it on. After it's done that once, i turn it off and back on and it starts up and passes POST.

Problem that just happened recently
Yesterday, it started doing this thing where my display would turn off and my fans would kick into overdrive. It did it in the past, but now it's doing it a lot more frequent (10-15 times in the past 24 hours). I was assuming it could be a cable issue just not being seated properly. I'm still thinking its possible. I've reseated all the cables one at a time but it never would get my computer to start back up. I'd press the power button and the fans would kick on full speed and would still have no display or POST success beep. Earlier, i realized that if I grabbed all the cables in the computer and slowly pull them towards the outside of the computer, the fan speeds would lower instantly and just turning the computer off and back on would make a successful POSt and my computer would boot up. This is so strange. I don't have anything else to test for faulty parts at the moment. I'm dreading to know the graphics card or PSU is going dead. Basically, the options I think are between the PSU, Graphics card, mobo, or a seating issue.

I think more than 1 opinion could help me out. Any ideas?