I had the same problem just a few days ago didn't seem to find out why it happened but what i did to fix it was, just dragged a new copy over from the 'Project map' to the 'View map' an it seemed to work.
Make sure you do this 1st before deleting the old perspective, as if you delete it 1st it will then make the perspective in the 'Project map' act up too, an i dont know how to fix that.
Once you have made the copy then delete or just leave the old perspective in the 'View map'.
Hope this helps.