The system preference panes will not load

When I open System Preferences and click on an item it says 'Loading Users & Groups' at the top of the window, but will not load the pane.

I've tried deleting the property list file:

 /library/preferences/com.apple.systempreference.plist 

I also tried clearing the PRAM and booting in Safe Mode.

Have you looked in the console? Maybe you'll find some error messages there which can narrow the problem down. You can view log files in Console, located in /Applications/Utilities.

Have you tried to check (and maybe repair) the file rights. You can do this with disk utility.

About Disk Utility's Repair Disk Permissions feature

Sometimes it's just enough to quit the System Preferences app. Check if the process was ended well, i.e. use Activity Monitor (also to quit "System Preferences" app). In my recent case it was not necessary to force quit, just select the process and quit was enough.

Alternatively Force Quit if System Preferences is open and in the Doc, just do a secondary click on the System Preferences icon, hit [alt] key "Quit" will change got "Force Quit" and click that.

After restarting the app the preference pane (in my case time machine pane) could be loaded as expected.

Lately it happened, that the described method didn't work, after force quit I still couldn't open the preference pane. I found that waiting a little (few minutes) before reopening helped, because when I was not able to reopen the pane I searched for a different solution, coming back to System Preferences – without doing anything else – was able to open the desired pane.

Boot in single user mode (Hold down SHIFT key right after hitting the power button until the Apple Logo appears), Login, Launch System Preferences, Load the Preferences Pane that is not working, Restart Mac OS X. That worked for me when nothing else did.