NTFS?
We upgraded the NTFS driver to something far more stable, and less prone to corruption. Unfortunately, this driver is far pickier about drives that have been improperly ejected.
The solution, if your drive is NTFS, is to plug it back into a Windows machine, run chkdsk /f on it, and then eject it properly and put it onto the ROCK machine.
We are looking into a safe solution that will avoid this chkdsk /f.