@kraker_abhy, Most likely a coincidence. What you describe sounds like a hardware problem, probably a loose magnet (you know that the N900 detects the back cover closed by a magnet sensor, right?). Either way the fact that a reflash has not solved it says clearly that it is not a Thumb problem and as such is off-topic in this thread. Please try posting in one of about a dozen "SD not recognized" threads or start a new one.