Problem booting to desktop

Hi, I've posted this problem on a couple of other forums, but no real luck and i was wondering if anyone here can help (first post!). I have this strange problem with my PC which is homebuilt with all new parts about 8 months ago. I press the power switch on and the PC boots/posts until after the Microsoft progress bar as normal, and then the screen goes blank, with the monitor saying that the cable has lost signal. Now when i manually shut it down and restart, it gives me the option to boot into safe mode which it does absolutely fine, so it definitely isn't monitor related. I have tried sfc/scannow and chkdsk but all is telling me that everything is running fine. I performed a memtest when i first built the PC which showed no errors. And the only thing i changed in BIOS is the Ram speed which I lowered due to mboard requirements. I did a bootlog but that didn't show up any anomalies that I could see. Im about to try uninstalling the gfx drivers to see if that makes a difference. I have looked at some boot problems others have had, but i can't find anything similar to this that helps.

Some system info;
Quad Core
Vista Home Premium 64
x48 chipset
4gb DDR3
4870 x2 gfx

Has anyone got any other suggestions? Im a bit lost as to what is causing this as it seems that it is all actually working fine, but can't display to a usable desktop!

Many Thanks