This information was provided by Claris Corporation on 16 March 1998, and incorporated into Apple Computer's Tech Info Library.
Error messages that you might see include "Application has unexpectedly quit with an error of type 1", or "type 11" (on the Power Macintosh computers) or the Claris application may just freeze and not generate an error message (in this case, the freeze is the error message).
Here are several things to try, with the pros and cons of each.
Lock the Claris Fonts file inside the System Folder.
Actually, the file could appear in the System Folder, Claris folder, Preferences folder, or application folder. Locking the file will prevent the product from attempting to build a new one. After you lock the Claris Fonts file, you should be able to launch the application.
Advantages: It's fast. It's reliable. It is easy. It's a temporary fix.
Disadvantages: The Font menu no longer appears in the native typeface. The bad font is still there and may cause problems later.
Restart from a Disk Tools disk, which would have a factory-condition font setup.
Advantages: It's fast. It's easy. It's completely reliable.
Disadvantages: This solution cures only the symptoms of troublesome fonts. After using the Disk Tools disk, you still have to troubleshoot to find the bad font.
Remove the offending font(s) and install fresh ones from the System disks.
Advantages: Most of the time, this is a reliable fix.
Disadvantages: It takes time to locate the offending font. You can test each individual font or try relaunching the application with smaller sets of fonts installed.
There's a great article in the Tech Info Library which deals with this subject, titled "Crashing/ Hanging when Launching Application." Although it was written specifically for FileMaker Pro, it is useful for troubleshooting problems like this.
Claris applications for Windows also create font menus in their native typeface. This article is titled "Understanding The CLARIS.FNT Font File."