I have a different cover with a similar issue; I had some grippy shelf liner similar to
http://www.amazon.com/Grip-Shelf-Dra.../dp/B000KFSOFI
I put a rectangle maybe 1 X 2 inches between the back of the eReader and the cover where the magnet is, and it works 95% of the time (if I press too hard it may turn off, but moving it away . I read others had put aluminum foil layers to solve it as well.