Really sorry you are still having problems. Nothing worse than spending money on new hardware only to realise the problems is still there. I only advised on psu because i to had similar problems on a HP machine with an ASUS MB. The PC would occasionally freeze and re-boot on occasions. This would happen more when using IE and on kids games sites. Tried everything possible eg new install, drivers etc. Eventually after about 3 months tried different psu and the problem went away. Opened up the faulty psu and found 3 bloated capacitors on the 12v and 5v rail. Replaced these and the faulty psu is fixed with no more problems. Really hope you find a fix. Like previous poster said please keep us informed.
I got news. I wasn't expecting a problem with the videocard because it was working fine for days in a row. Seen a lot of faulty videocards but they had other symptoms. Borrowed a simple videocard with G100 chip. Took me a while to find someone that had a spare. On thursday 6th I replaced the card and installed 310.70 drivers. Now on sunday after 24/7 use, it is still working fine. Even some issues I had with the mouse are gone. When selecting a part of a sentence it took 3 attempts to finally could do what I wanted. Thought that it was a Windows 8 bug and was waiting for updates that would fix this problem. Now working on the PC feels smoother and whole perception of Windows 8 have changed. Really hope this is solved. The new hardware is good to have around, so no worries. Consider this as an upgrade. Will stay in touch.
Of course the borrowed card has to go back, so I bought a second hand 9600GT passive. Installed this afternoon and indeed keep my fingers crossed.