This can sometimes happen when the choice to import DP3 preferences is selected on the DP installer.

Try trashing DP4 preferences with the following steps:

1. Be sure to Quit all applications (especially Digital Performer).
2. On your Mac hard drive, open USERS > your "home" icon (whatever you named your computer) > LIBRARY > PREFERENCES.
3. Inside the PREFERENCES folder, locate and open the folder called Digital Performer.
4. Inside this Digital Performer folder, locate the item "Preferences" and drag it into the trash.
5. Restart your computer, launch DP4 and reconfigure as needed.