Resetting your Protégé preferences may fix certain problems with initialization and display of data.
Occasionally, corrupt preferences prevent Protégé from starting and/or properly displaying entities. In particular, the default font or the look and feel can get set to something that does not work. Resetting your preferences will return the following items to their default state:

- entity rendering
- recently visited files and directories
- look and feel
- inferences shown when a reasoner is started

After a reset, restore your preferences from the File | Preferences... menu.
IMPORTANT:

- Please close all other copies of the Protégé application before resetting your preferences.
- Pressing the Reset button will shut down this copy of Protégé. Restarting Protégé must be done manually.