The Demo still has quite some bugs, I'm sure the full version would work flawless.
Which means you'll have to consider if you want the game without having played the Demo.
Maybe you could watch some game-play videos.
You could also just reinstall the Demo and see if that works.
Further, you could post the last bit of debug.log which is in the Aquaria directory, but I'm not sure if that's there in the demo.