What do you mean by this? Can you run a sample jME project? (The one with the blue cube)
Assuming you have a Nvidia graphics card (and that you already tried all proprietary drivers you can), can you try using the Nouveau driver? (You can select it by going to the Dashboard and typing “Additional Drivers”
Also are you trying to launch the game in fullscreen mode? I’m having a similar issue, but in case you are, try launching in windowed mode (which works for me).