This kind of thing tends to happen when your optfs is corrupt. Did you by any chance force power-off in the past few weeks? Long power button press, pull the battery out, battery ran out in the middle of doing something... Your chances of recovery range from easy as pie to nigh impossible and it is hard to tell which. If you have BackupMenu or at least SSH installed then you might have a fighting chance but if not, then you are stuffed. Reflash might be your only option. Hope you have a backup. Sorry.