In february I got this hard drive: http://www.amazon.com/Samsung-Statio.../dp/B002C46042 (Samsung Story 1TB) I plugged it into my Mac, made it OS X Extended, and it worked great. It has 500GB on it. All of a sudden it became Read Only, which prevents Time Machine to perform any back-ups. The Mac forum suggested I format it, but that's only for NEW drives first connecting. I've had this for almost a year working fine. It's no longer showing up as an icon on my desktop or in Finder. Disk Utility shows it, but all the options to repair disk are greyed out. Please help!