Thanks Satcomer, but that didnt help either, since the problem is not with the root user, but with my personal account, and the root user was not able to change my profile either.
But I found the solution to my problem to be pretty easy to implement, after I found this thread in Apple foruns:
http://discussions.apple.com/thread....597&tstart=150
Quoting the solution described by donv (The Ghost):
"Try this solution. If it doesn't work, then we can think about reinstalling.
Go to ~/Library/preferences/ByHost/ and delete all com.apple.HIToolbox files.
Restart your Mac.
Go to your user account preference pane.
Unlock the lock
Type your password.
Lock the lock.
Try installing whatever you are having problems with again. "
And it worked great. After reboot, when I clicked on the lock, it prompted for my user and password, and the lock when unlocked. After that, everything worked great.
I thought I should share this with everyone in this forum.
Thanks.