Weird mission control problem

Whenever I activate mission control and then deactivate (to return to the desktop) it automatically switches to a different program. For example, I will have safari open (in the background) and will also have mail open as the active window. If I activate mission control, don't move the mouse or touch anything, and then deactivate mission control, safari will automatically become the active window and mail is hidden behind safari.

I have tried changing all types of settings and even reinstalled lion, but nothing works. Does anyone know why this is happening? Is it just a bug or am I the only one experiencing this?

Thanks in advance for any help!