ATI`s do have heat issues, If possible leave 1 or 2 slots open below the card and leave out the PCI covers to allow air to pass out the rear.Ive even went as far as mounting a fan that will push air across the card and out the open slots.I have a AIW 9700 Pro card that i actually replaced the fan on i used 1 of the fans from a Hard Drive Cooler .It didnt bolt into the heatsink cavity but i found the proper lenght of screws and mounted it to the heatsink centered above the fan cavity.
I would run memtest overnight to rule out any memory issues.
Prime 95 is another tool to use for testing hardware overnight .
I run my ATI card on 1.5 volt setting in bios. Check and see if disableing FastWrites in the ATI CP helps .
Thermaltake Armor A90
Corsair HX1000W PS
i7 2600k / Cooler Master Hyper N 520
Asus P8Z68-V Pro / Gen 3
8 GIG Corsair Vengeance
eVGA GTX 570
SB Audigy2 Platinum
Kingston Hyper X120 SSD
WIN 7 - 64b
LG Blue Ray Super Multi Burrner
Logitech THX Z560
3x120mm - 1x200 mm case fans