Did you use driver cleaner after removing the Nvidea drivers? Theres potentially a driver conflict if you didn't. I just opted for a fresh install when I switched from Nvidea to ATI-bit extreme but didn't want to take any chances.
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Xeon 3350/E6750| DFI X38 LT| 2 x 4870|74gb Raptor
Thermalrock Dragon Case (sprayed black)
CPU loop: MCR 220 int.|Apogee GT| MCP655
GPU loop: MCR 320|Swiftech Res.|2x EK FC blocks| MCP655.
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