Had the same problem with release 2011. I have to click several times on ribbon buttons for the command to become active. There was at least one other person suffering this behaviour, so I'm not alone.
I remember something similar with release 12, way back when digitzier tablets where in fashion. You had to move the puck at the time you clicked one of the buttons. If you kept the puck steady, clicking the buttons had no effect. Pretty annoying as I recall. Now something similar with 2011 and 2012.
Tried several things, like different mousedrivers. The Aero-theme is already switched off - in fact, the Themes-service is switched off alltogether.
When I switch to the 'classic' workspace (i.e. 'ye ole toolbars) everythings works fine - I don't have to click toolbar buttons several times before they become active. So when I'm fed up with clicking ribbon buttons in vain, I switch to the 'classic' workspace.
BUT - I just want the Ribbon to respond without hesitation. Any clues?