"New" gpu unbootable

[pitastrudl]

So i have a
mobo: http://www.gigabyte.si/products/product-page.aspx?pid=2695#ov
psu: Corsair VS650
old broken gpu: ati radeon 4870 HD sapphire
new one: ati radeon 5850 HD Radeon + arctic cooler

Bought the gpu second hand, tested the gpu on his pc, also running a benchmark, everything worked fine. Put it into my pc, on boot there are 3 beeps, 1 long 2 short. Wouldnt boot, I tried turning off the pc, switching off the PSU and wait a few minutes, then turned on PSU,waited a few mins and turned on pc. Same beeps. Now the thing is it started once, and i managed to get in. update drivers, reboot and it booted twice without a problem. Then i started up a game to see how it worked, and after loading up the game, the pc froze and i had to hard reboot it. After that i tried 3 times to boot it and same beeps occuring.

The mobo manual says the 1 long beep 2 short is monitor or graphics card error. Also the card is pci-e 2.1 and my mobo has 2.0 slot so im not sure if it's that.

 

[Calculagator]

It could possibly help to update your bios to the newest version if you haven't already. PCI-E versions shouldn't make any difference.
With such a large cooler, the GPU could be loose in its slot: you should make sure it is fully seated and not sagging.
Your PSU should be powerful enough, but if it is old, it's possible that it's not quite able to keep up with the power draw when you first turn everything on. The 5850 was a beast and with a custom cooler is probably even more so.
You might also check to see that nothing else was bumped loose when you installed the card.