Strange Radeon 4850 problem

Hello, my friend just bought a new heatsink and fan for his cpu because of heat problems and he's installed it correctly according to the manual. However now his graphics card wont work correctly with 2 lights on the back flashing or either on (depending on how he configured the power cables)

his system is

£252.16 x 1 - Hanns.G HG281D 28" Widescreen LCD Monitor

£93.90 x 1 - Gigabyte GA-MA790XT-UD4P (Socket AM3) PCI-Express DDR3 Motherboard

£69.56 x 1 - AMD Phenom II X2 Dual Core 550 3.10GHz Black Edition (Socket AM3) - Retail

£68.69 x 1 - Asus ATI Radeon HD 4850 512MB GDDR3 TV-Out/Dual DVI/HDMI (PCI-Express) - Retail

£57.38 x 1 - Corsair XMS3 DHX 4GB (2x2GB) DDR3 1600C9DHX Twin3X (TW3X4G1600C9DHX)

£47.82 x 1 - OCZ ModXStream Pro 600w Silent SLI Ready ATX2 Modular Power Supply

£33.90 x 1 - Seagate Barracuda 7200.12 500GB SATA-II 16MB Cache - OEM (ST3500418AS)

£23.99 x 1 - CIT 1003 Gaming Case with Side Window - Black (No PSU)

Seagate 320GB SATA II

The new heatsink is a Tuniq Propeller 120 CPU Cooler and before he just had a standard fan and heatsink.

The lights on the back of the graphics card are called D1601 and D1602. Sometimes we've turned it on and it's just been a constant light, other times as I mentioned before it flashed.

Any idea what the problem could be? I can't imagine why a graphics card wouldn't work because of a new cpu fan/heatsink installation. However he did take it out to clean the card whilst he was there but I dont think he damaged it because he used a pressurised can.


Any help would be greatly appreciated!