Symptom
Once Muk3D is launched from Catapult it starts to load and the splash screen appears, but then it appears to exit.
Cause
The muck3d.ini settings file can become corrupted.
Solution
Open Windows Explorer and go to c:/Users/<your-user-name>/AppData/Roaming/MineBridgeSoftware and rename the file muck3d.ini to muck3d.ini.old.