Zen Bounds 2 - Windowed mode, very slow, unplayable

[Hybr1dz]

OS: Windows 7 x64
GPU: 320 MB Geforce 8800 GTS (latest drivers from nvidia)

After installing Zen Bounds 2, the game starts up perfectly fine and I can play it in windowed mode without a problem. After I exit the game and try to start it up again, the game slows to an extreme crawl. I can hear the music but I have to guess that it's rendering 1 frame every 20 seconds. It's so slow that I have to terminate the game through the task manager as it never made it to the main menu. I uninstall the game and reinstall. Again on the first start up it runs perfectly fine and then after exiting and re-entering the game, it is extremely slow.

Anyone else with this problem? Any help is appreciated!

Update: Looks like if I set it to full screen it works fine now even after I launch it a second time. But for casual games like this, I'd prefer to play them in windowed mode.