One strange thing I noticed after updating my drivers and checking the display tab in dxdiag on Windows 7x64, was that my DDI version displayed 10.1 instead of 11. Fortunately I found a fix from Microsoft which returned it to 11 but the problem still persists. I have tried numerous Catalyst drivers such as 10.9, 10.10a, 10.10d and 10.10e and they all have the same problem in DX11. This issue did not exist before updating from 10.10.
For the record, I have performed a clean install of the above drivers and uninstalled my old drivers thoroughly by using Driver Sweeper.
While the game runs fine in DX9 I prefer the increased performance DX11 provides and very slight graphic enhancement to water reflections. If anyone can provide a solution I would be most grateful as am at a complete loss as to what it can be. It's even more confusing as Dirt 2 runs fine in DX11.