31370: Mac OS: "Can't Open Preferences File" Message covers what to do when a Control Panel's preferences becomes corrupt. The short answer is, trash the offending prefs file.

The Accounts System Preferences pane may not be the most glamorous destination in Mac OS X, but it?s definitely worth a stopover in Leopard (Mac OS X 10.5). Check it out and you?ll find a ...

If that happens, never fear—open the preferences file in a text editor, such as TextEdit. Look for these lines: ...