Maybe it's a Disk checking probleme,
I'd same probleme with RB 7.2.1,
i plug the disk on PC and make a chkdsk or disque checking, it's say me no trouble found,
unplug properly the disk with eject it
and replug them on RB and after all thing return in normal place
i thing some time the disk don't land correctly or you shut down to rapidly RB
it's my 5 cent idea and it's work for me but cant know if it's same thing for you
Cheers