Overheating with Saphire HD3870

Hi, long time lurker, but been having some problems lately so i decided to register

1st off system specs

550W PSU
2 gig ddr2
amd athlon x2 6000+
1 320 gig SAta Drive
mobo; ECS GeFroce6100SM-m2 (I know **** mobo I was just too broke to update it when I updated the rest of the PC)

When I got this card, I was very happy with it. Ran everything I could throw at it at high settings. I wanted to see if it can overclock, but I didn't get much success with it, so I'm running it at stock speed. But after the overclocking business ( I only tried OC with the auto tune) I got less performance out of it @ stock speeds.

anyways, to the problem. I still play C&C Zero Hour with this mod called Shockwave (also increases graphics quality) and the card overheats at random. By random I mean, sometimes i can play for hours and not get it or I get it after 20 mins of playtime. This also happens with UT3 on high settings. But I don't get overheating with COD4, Supreme Commander nor crysis.

I have the fan set on at least 60% at all times, and my normal temperatures are 35-45 at idle and 60-65 under load. But with UT3 and Especially with Shockwave, it goes upwards to 77-80 degrees (even with the fan @70%) and the screen goes black and I have to restart.

Can the motherboard be a problem?

Could the card have been damaged when I tried to OC?

or could be simply the heat sink not seated properly? (not sure if those temps are normal)

possibly a combination?

Another thing, would the PSU not supplying enough power on the 12v be the cause of all this? I had it running on a lower PSU but that PSU died; turned out it was running with 20amps on the 12v. so I bought an adequate PSU, but the card might be damaged already?

Thanks in advance

Yeah its not exactly name brand supply, Noma, the guy I bought the other PSU from that died replaced it for free, so I took it.

CPU temp never goes above 45-46 Celsius. and for the 3870 im pretty sure that 80 degrees is pretty high.

I forgot to say, sometimes I don't have to restart the PC, but the VPU recover kicks in, so I'm pretty sure its the card overheating. As soon as I can check the temp on the card after a lock up, its always around 80 Celsius, no more.

I don't really know what to do though. Last time this happened the fan was running at 75 percent, fixed, and it still heated up. I raise the speed any more and the noise of the fan is just insane. after around 45-50 % the fan gets audible, and after that it just gets worse. Before I could run the fan at 30-35% and I wouldn't have overheating. It started with shockwave, then with UT3 and its more frequent and with higher and higher fan speed settings