7800 gtx crashingFollow

Ok I am completely baffled at this problem so hopefully some of you techies could help;

I have an AMD64 (4000+ I think?) CPU and an XFX 7800GTX card.

On quite a few games (Crysis, Universe at War, Unreal Tournament 3) games would tend to pause for about 30 seconds with the music still playing in the background. After which the game would either resume with HUGE performance reduction or I just get fed up and restart -.-

I also hear my fan speed up when my computer is getting busy, the weired thing is I had a CPU temp monitor thing up once, and noticed at full load my CPU temp remains pretty close to 50 degrees, so I thought fair enough, can't be the CPU overheating right?

So I thought maybe it's the GPU?

I monitored the GPU temperature, no games running ant it's at an average 70 degrees or so...full load it reached just over 100 at one point!?

I haven't over clocked this card at all or my CPU, everything is default.

I went to XFX's web page and checked their default clock speed for my card and checked an over clocked version also.

Normal 7800gtx: 450
Over clocked 7800gtx: 475
Even more??: 490

Mine by factory default was at 475, ok so I thought fair enough, let me try reduce it to 450.

Tried Unreal Tournament 3 again and it crashed even quicker?! That completely got me confused and I gave up -.-

If anyone could give the slightest glimpse of hope before demanding my graphics card being seeing it's final days I would be greatful.

I don't know what other details you need me to provide but let me know~

Thanks in advance.