Having a corrupt font installed on your computer can make certain application or your system itself go a little wonky. There are 3rd party apps that you can buy to detect corrupt fonts, but did you know that the same functionality comes with OS X 10.4, Tiger?
Simply launch Font Book (it’s in your applications folder), and select the fonts you want to check (command + A, to select all fonts). Then, select “Validate Fonts” from the File pull-down menu. Font Book will tell you which ones passed, looked suspicious, or down right failed. You can then delete bad fonts by clicking the box next to it in the list, and clicking “Removed Checked”. That’s it.
Found via Apple’s Tip of the Week