Team BSOD : Unexpected BSOD results in crash dump

Hello everyone I have had BSOD's occurring on a relatively frequent basis (one every 1-2 days), and have been unable to diagnose the problem. Computer was running fine for about a year before this started occurring. I am hoping it is just a driver issue of some sort, but in the absence of any real knowledge about these things I have uploaded the minidump file in the hope someone can tell me what the issue is.

My comp specs and operating system (if it helps) are

I5 2400
4gb DDR3 1333 Mhz
ATI 6850
Win 7 64 bit

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