The error code given was 0x0000007E
I did some searching on this one and it could be caused by a number of issues (inlcuding bad ram)
After yet another reinstall of windows I soon started getting the error code 0x00000050 instead. This is more specific a ram issue.
I took the twin RAM-blocks out and installed them in the other two ports. After several hours it now seems to be solved whatever it was. (error on the port itself, bad connect, ?)
The plus side is that I found that these two new slots recieve a hellavu lot more air flow from the 120mm CPU fan.
Not that I think it was a heat issue. They should be able to run with just passive cooling at default clocking, right?
I shouldn't have to up voltage as long as I don't overclock, should I?