With my soverign and a scout standing on the same tile I hit the TAB key and the screen scrolls to the lower-left corner where the compass is (and the compass seems to disappear).  Hitting TAB again goes back to "The Soverign's Army".  I have no other units on the map - though a squadron is inside my captial.  I was trying to cycle to the captial (which TAB normally does) and discovered this bug.

EDIT: Even after moving my squadron out of the capital I still only can TAB between the lower-left corner and the Soverign's Army.