I have the exact same problem as the OP, I've tried the same things but without any luck.
I uninstalled an HD6870 and then installed a HD7870, CCC worked before but not now.
The divers work fine it's just CCC that wont load, I really don't want to have to reformat just for the sake of CCC.
Has anyone managed to fix this problem ?
W7 ultimate 64bit, Q9450, Gibagyte GA P35-DS3P