My System Preferences controls are dimmed
Many of Mac OS X's control panels are off-limits to Standard account holders. Even if you're an Administrator, in fact, Tiger requires you to unlock System Preferences the first time you open it (by clicking on the padlock icon at the lower left corner of System Preferences and then entering your password).
I can't log in! I'm in an endless login loop!
If the standard Login screen never seems to appear - and you go straight to someone else's account every - it's because someone has turned on the automatic login feature...
You won't have a chance to sign in with your own account until somebody Logs Out. (Apple Menu - Log Out)
I can't move or open a folder.
Like it or not, Mac OS X is unix, and Unix has a very strict sense of who, among the people who share a Mac over time, owns certain files and folders. For starters, people who don't have Administrator accounts aren't allowed to move, or even open, certain important folders.
So how do we fix that?
First Resort: Repair Permissions
An amazing number of mysterious glitches arise because the permissions of either that item or something in your System folder have become muddled—that is, the complex mesh of interconnected Unix permissions.
When something just doesn't seem to be working right, open your Applications>Utilities folder and open Disk Utility. Once there, go to First Aid and click on Repair Permissions.
Second Resort: Look for an Update If a program starts acting up immediately after you've installed or upgraded to Mac OS X 10.4, chances are good that it has some minor incompatibility. Chances are also good that you'll find an updated version on the company's Web site.