In the master page (Right Side/Odd numbered pages) I have a graphic but when I over ride it and try to delete it, another one is automatically generated. Strangely, if I do the same on the Left Side its all fine.
Okay- Mystery solved. I had made the graphic on the left master page then copied it on to the right master page. Somehow, it was still technically attached to the left (even thought it was not on the left at all).
When I redrew it on the right, I was then able to delete it. I don't know why, but that's my story. Hope this helps someone else.