Almost certainly a driver issue of some sort.
Cas

I heard other ppl also had the same problem. So is it a bad driver for the graphic card or for the display and is there no way for me to work around it?
If it is correct what you are saying then I should thank you very much because else I would probably spend alot of time (which I already have) bumping my head against a wall if I think it is the Java code fault.
So, is there no way to see that alt+tab coming and quickly set the full screen off before the alt+tab comes into effect (also tried it but never go it to work)?