LWJGL graphic of my project doesn't work correct on my iMac - HELP

[TKPROG]

Hi to all developers!

In the last week I got a big problem. Whenever I started my game out of eclipse on my iMac (Mac OS X 10.7.3, 16 GB 1333 MHz DDR3, 3.1 GHz Intel Core i5, AMD Radeon HD 6970M 1024 MB, Mid 2011) the game didn't work correctly. I made a video about this, you can see it here: http://youtu.be/746qc_IYCxk

You see the gamescreen? It is black, but it should look like the screenshot in the attachment...

After I saw this, I tested an other project i made before and it worked.
Then I sent this to a friend with the same iMac and there it didn't work, too.

In this fact I think I am starting the game in a false way. But on my Netbook (DELL Latitude 2110, 2 GB RAM, 1,83 GHz Mono Intel Atom) it works everyday (Because I am coding on it ).

I googled it everyday since I got the problem, but there were only problems about Minecraft and other stuff I don't need.

Now my "question": What should I do? What do you need to help me? Code, or other things? Please help me!

Thank you for reading and maybe for answering.

Your TKPROG

PS.: The game is going to be sold for 0,-$ ^^ http://tkprog.square7.ch/MeusDorfusII/