magic mouse battery cover stuck

I've found the solution to this problem. Instead of trying to pry off the metal cover, use a tool (I used the tip of a small screwdriver) to pry off one of the black strips on the side of the cover. That will loosen the cover so you can change your batteries. Once you've inserted the batteries, carefully replace the rubber strip. It has to be snug and snap into place. Then simply replace the cover and turn on your Magic Mouse to connect.