The temperature has never been anywhere near it's operating temperatures simply because of the bigass cooler.
What's the point in disconnecting stuff and seeing what happens? The problem occurs when the PC is under load, IE playing a game, so I wouldn't be able to do anything like that to test it.
Well it might be a feature on my Mobo that when it's underpowered it drains power from the PSU or graphics card, i'm not sure now whether it's actually throttling or not, but it'es definetely draining something, like the graphics card.
Before I had an old ati 128mb card and moved up to a 8800gts 624mb card the pc done the exact same thing, would play for a while then would drop to around 10fps. I put in a bigger PSU and it was fixed, now I have the exact same problem and putting in a slightly bigger PSU actually helped the problem but didn't cure it completely.
So i'm pretty sure it is the problem, I was speaking to a pc boffin friend who said every PC he's been building or helping build has had no less than a 600w PSU in it, simply because the new processors are so power hungry.
Anyways, i'll try something, maybe find a bigger PSU to try in it and see if the problem persists.