ATI Radeon 4870 - Blue Screen

For the last few weeks my computer will shut down occasionally and I get the following error message. The screen has lines through it during the error and some parts are blocked out in white. Vista tells me its the driver but I'm beginning to doubt it since I've tried 4 different driver versions.

The problem seems to go away if I turn my computer off for a few hours --- do I have a heat or hardware issue? Any thoughts appreciated.

Problem signature
Problem Event Name: BlueScreen
OS Version: 6.0.6001.2.1.0.768.3
Locale ID: 1033

Files that help describe the problem (some files may no longer be available)
Mini091309-01.dmp
sysdata.xml
Version.txt

View a temporary copy of these files
Warning: If a virus or other security threat caused the problem, opening a copy of the files could harm your computer.

Extra information about the problem
BCCode: 116
BCP1: FFFFFA8006E9C010
BCP2: FFFFFA6002E337E0
BCP3: 0000000000000000
BCP4: 0000000000000002
OS Version: 6_0_6001
Service Pack: 1_0
Product: 768_1
Server information: 44ebb93a-3648-422f-8fa9-564310aea46d