Games that change the resolution can often have unexpected effects when you exit. Try restoring a snapshot:
To restore Fences to a previous snapshot:
-RRight-click on the desktop and select "Configure Fences..."
-Click on "Layout and snapping" on the left hand side of the configuration window that appears.
-Select a snapshot you wish to revert to. A preview window will appear showing you what the desktop will look like.
-Click Restore Snapshot to revert the desktop to this preview.