The same thing happened to me - it really is just stuck. So working out wouldn't help. I used two rubber jar openers - one to pull the top of the case and one to pull the bottom of the phone.
I used the Invisible Shield with the Incase slider and it messed up the film around the camera. Pushed it down and now it affects the camera flash. Gotta remove the Incase to remove the back film as I purchased cheapie ebay ones. lol. Way to ruin a $30 film