Horizontal line appears in fullscreen mode

I have an issue when entering fullscreen mode in any application on my MacBook Pro with OS X 10.7.3, a white horizontal line always appears at the top of the screen (as shown in the picture).

What is causing that? I've never had it before and I can't figure out what I've done to cause it. Anyone that got the same issue or know what's causing this?

Solution 1:

Do you have and programs running such as VMware or Virtual Box installed and running in Full Screen Mode in the background? It alsmost looks like a VM or remote desktop toolbar. Have any programs running that have tool bars such as pictured below.