When I load MSI afterburner you can change your maximum clock speeds etc, but there's no way to force the minimum.

Anyway, I seem to have ATI Tray Tools working at the moment.
Right click on icon in tray
select Hardware, Overclock Settings
Drag core speed to your standard max (880 for me)
Increase voltage with the drop down selection (1.175 for me)
Hit Apply
Play game
Go back into overclock settings
Hit 'Set Default Clocks' (instead of trying to set them back manually, which was causing me problems)

My clocks don't clock up for Cliffs of Dover, so I have to force clock settings using MSI Afterburner. The unusual pseudo-fullscreen mode used by the game seems to be causing problems for the drivers. This is not surprising as most DirectX games are played traditionally in a full-screen mode as it offers the best performance.