mine creaks too...on the bottom two corners, not the top two. I took it into the MSFT store in Bellevue and the3 Asst Mgr asked one of her compadres to get another XL and they swapped back covers top see if the cover were the problem, not the body. Alas, it was NOT the cover. She offered to swap phones but had none at the time to do it with. I will return when they have phones to cover returns. I do have a Mozo on order, may wait to see if the thicker stiffer back cover solves the problem. If not may go thru the tape or drop of glue trick.