I got this just about two weeks ago. If it's an E 68 then it's your hd. I just had to buy another one yesterday.
That's 4 Xbox's, and 2 hd's. Sweet. I've seen vid of people fixing the problem by removing their hard drive, shaking it and tapping it on shit, putting the hd back on and the thing works fine. Also if you throw the switch on the a/v adapter coming from the back of the box, this has been known to work also. Just flip it to tv or hd, whichever you're not using, then switch it back. The Xbox should reset itself.
None of those worked for me though. Good luck!
Am I the only one who finds it shady that all these hd failures are happening at the same time?