Quite possibly coincidental but now a real annoyance. After updating from JF3 to JM1, after reboot I was advised that my 32gb external sd memory card was damaged. I took the card out of the phone and tried it on the PC and it performed accurately with all of my information accessible. I copied the files on to the PC and reinstalled it into the SGS. Whereupon again I was presented witht he error message. THe card appears dead to the phone with the only remaining option that in not greyred out regarding the sim card the "format" option. I tried this and the card became visible again tot he phone. I then copy back over all my files which takes a couple of hours. Everything performs as you would expect, until.....you turn the phone off. Whereupon it does it's media check and pronounces that the memory card is damaged and the whole reformat, reinsall cycle has to be initiated again. Really quite tedious. Has anyone else had this problem and know how to fix it? I should add a couple of points, the phone is not rooted and the error message did not appear with JF3 for the 3 weeks it was running this firmware. I look forward to your comments and suggestions.