ive got windows 7 with a 4850, its worked perfectly fine through beta, rc1 (7100) and the final (7600)
just if you did an upgrade from vista it somehow screws up ccc.
another problem ive had is ive installed ccc, used windows update and it says it has an update for my driver, i update it and it screws up ccc
if all that doesnt work try downloading the drive and ccc seperately (on the download page it has catalyst components all the seperate stuff)
if that doesnt work try a reinstall of windows