Sounds like a dodgy HDD problem or a usb driver problem on PS3, have you tried copying videos and pictures from a media server app running on a PC, just to see if its USB related or HDD only. also try an app like comgenie filemanager, this works on a lower level without needing xmb files so it might work if its a firmware issue. Also maybe your file and folder permissions have been messed up, try look at file permissions by copying some files to PC if you can and checking . Strange issue... good luck with it. maybe a previous payload created some wierd file permissions, I did hear of a permission fix pkg but I never needed it myself so havnt researched it.