Syst pref sticks on "authenticating" after PW


I cant change my system prefs.....i hit the padlock give my admin password then it says " authenticating....." and just sticks there..if i close prefs and reopen then the padlock is greyscale and i cant click anything..ive reinstalled and got same problem HELP!! thanks:confused:
its a home personal computer so im the only admin....any suggestions?? its a real pain cause its set to sleep after 5 min and its driving me nuts plus i cant change start up disks and important stuff lie, that ack help!
i did the fsck-y thing and all was the clean install under custom install?? i dont seem to remember seeing that option..also if i didnt back up what exactly gets lost re other datawise..everything?? nothing unless something crashes or just the new stuff on my osX or any of my 9.1 stuff?? sorry for the questions but your a wonderful help
small question,
did it hang up on the candy-blue screen ???
I've had that happen to me... I just forced rebooted and it was useable, but then it hung up on doing some task...forced a reboot and it seemed to work fine....