Risa, I used to have this problem with my ferrets.  I can't really explain
why they would move the litter box an poop behind it, but I can tell you
how I solved the problem.  It was recommended to me that I totally
re-arrange the cage every so often.  Move the ramps/ladders, shelves,
bedding, food dishes, water bottles, and litter pans!  EVERYTHING.
Completely clean the cage with soap/water or whatever you use to clean.
My ferrets stopped using the wrong corners.  Now this was not a permenent
fix, I have to re-arrange the cage about every 2-3 months.  However, it
stops them every time.
 
Maybe my ferrets are just wierd, but it's food for thought.
 
Natalie and the *3* furry snakes
[Posted in FML issue 3457]