If you are still having problems.. This could also be part of the culprit
I see system specs for you that you have
Graphics CardDiamond Radeon 5770 1GBI have the XFX card, But still doesn't matter.. There is a timing issue going on with the Graphics cards and Windows 7 when the card goes from high to low or low to high power states.. It seems to happen randomly and often you won't get a crash dump, it just freezes.. I also had the Ram voltage and timings issue.. That was just half the problem.. Look on majorgeeks websight for ati tray tool,
http://majorgeeks.com/ATI_Tray_Tools_d4569.html
This will help. Be conservative with overclocking.. Because you are going to lock it at that clock setting so it doesn't keep going low , high, low, etc power states..
This is going to be even more of an issue with new web browsers using accelerated graphics.. Hope ATI makes a real fix soon!
also, make sure you check your operating system integrity by opening an elevated command prompt.. ie: in search box, type CMD then right click it and run as Administrator.. Type in sfc /scannow system file checker will attempt to fix any bad items and you'll see where it saves a log file. If it cannot fix then think about re-install if windows repair doesn't work.