thats really strange i havnt had this happen yet...keyword...maybe it wasnt signed correctly or something became corrupted in apktool...try downloading the drag and drop sign tool from xda-developers forum(its bundled with a few other things downloaded a while back dont remember exact name but should be easy to search for) then take to recompiled app and drop it onto "drop_and_sign.bat" and it will sign for you and spit out the new one in the same directory...if this doesnt help then possibly you altered something and didnt realize it...