Fullscreen Gui Bug?

Hi all,

I have a big problem. My game uses new unity gui and I have problem with full screen in standalone build (windows).
Problem is on image below. My mouse must be in different position than the button for interact with it.
This problem is in full screen only.
In window or in native fullscreen resolution all works well. How i Can solve this problem?

Thanks for all ideas!

My version is: 5.1.1p2 personal