Print Center is a bit buggy and messes up files causing error messages and an inability to add printers. You get errors like:
An unexpected error has occurred. -108 An unexpected error has occurred. -9621The rest of this is probably obsolete since Apple has released an application to clean up the file priviledge issues that cause problems for Print Center. See their article and download the utility. You probably won't need to run print center as root, but may need the PrintingReset app.
0. Apple is aware of some issues, and has trouble-shooting info on AppleCare Document 106714. But, this does not fix everything, and it seems that if you run into these issues, it messes things up beyond easy repair.
1. There is a gui tool specifically to fix Print Center, called Print Center Repair from fix-a-Mac Software. You need to register before it will work. However, the web page contains a nice article describing what needs to be done, much of which you can do manually from the command line.
2. The essential fix is to run a hidden program bundled with PrintCenter that resets things. The rest can be worked around simply by running print center as root. I don't know how you're supposed to know about this, but here's what to do:
% su password: # cd /Applications/Utilities/Print\ Center.app/Contents/MacOS/ # PrintingReset # Print\ CenterNow you are in Print Center as root and should be able to do everything you need.