The only time I came upon this was when I accidentally changed all the file permissions on the drive. It may be best to ask at the InsanelyMac ( http://www.insanelymac.com/ ) forum for an answer to this problem.
I had a backup of all the data that was on my Mac so I just reinstalled Mac OS X and then installed my apps.
I had a backup of all the data that was on my Mac so I just reinstalled Mac OS X and then installed my apps.