Whenever I try to fullscreen Spiral knights, the game poofs. Just vanishes. I can still here the sounds, but and I can see Java running it in task manager, but It isn't really there anymore. It's extremely annoying.
Running Windows 7 ( 64-bit ), newest Java update, latest drivers for my Geforce 520.
try manually changing it
Go to number 5
http://forums.spiralknights.com/en/node/48