Buttons keep flickering.. help?

Hello, I’ve made some butons but when you go over them
with your mouse, the cursor keeps flickering, it’s hard to click on the button. I tried to modify the hit state, but this doesn’t seem to work. I’ve tried finding the answer online, but I can’t find it, maybe you guys can help?
You can find the button here
http://www.himalaya-centre.com/

The little person in the left corner that is doing some exercise seems to move much faster on a different computer then on mine, how can I change this?

Grtz Eva