Quote: "the problem comes when you want to upload a 3D model in the program"
This could be the model causing the issue if its third party......
Try one from GameGuru itself..... Wont do any harm it will just import it to the "user" folder in the entitybank.
If that works fine it could be the model you are trying to import ?
The only person ever to get all his work done by "Friday" was Robinson Crusoe..