Full screen mode does not overlay all elements in Required Properties view

Description

When creating any page / block containing an XHTML property using TinyMCE version 2, if the editor uses full screen mode while in required properties mode, an element of the Episerver interface overlays the editor window.

Steps to reproduce

1) Create a page / block type containing an XHTML property configured to use the full screen TinyMce plugin.
2) Mark the property with a [Required] attribute / mark it as required in Episerver Admin mode.
3) Create a new page / block of that type.
4) Use the full screen tool bar button.

Expected:
The new block area should not be visible.

Actual:
The New block area overlays the text editor window.