I woke up Sunday morning, put in a backup and my 360 brought up 'open tray' on every DVD, original, backup, CD ect that I put in it.
It was working perfectly up until then.
Didnt run any game updates, hadnt changed firmware since v1.1 (a good few weeks back) and hadnt even moved the 360 from the table. Only ever play it for up to 1.5 hours at a time.

No spin up, just 'Open tray' Literally 1 second after the drive closed.
If you put your ear to the drive you can hear a faint click right after the tray closes and thats it.
It doesnt even try to spin up to attempt to read anything on any disc.

Tried restoring the firmware - no change
Tried flashing to the latest 2.0 firmware - no change
Tried flashing to 1.2 - no change
Tried adjusting the pot to 3.4 - no change
Then to 3.0 - no change

I dont think there is anyting else I can do is there? Im not confident in buying another drive if this could happen again...

Can it just be that the laser has packed up? or could it be the mechanism that spins the disc?

??????????

I got the exact same problem with my hitachi. I was playing a dead rising backup when I got a dirty disc error message, Since then the 360 won't start any original or backup games. Either it just displays "open tray" or it tries to read the disc and won't stop trying, doesent display unrecognized disc message or anything. PLEASE HELP ANYONE!!