my room mate has the same problem and his way of getting it to work might not be the best or the safest but it works. If you beat on it not that hard but like knock on it over the DVD drive then it will sometimes knock the magnets back to where they are supposed to go. Recently he has been opening and closing the tray fast and after a few rotations he will stop and every once and a while his game will play.

The way I fix mine was a little more drastic as I took mine apart since I was going to jtag it until the new update came out. But with it apart take out your DVD drive and take the 4 screws off of the bottom of the drive and take the top cover off and see if the magnet from the actual tray is stock to the CD hold down ring if it is take the magnet off of the top and superglue it back in place. For me since I have the Benq drive in mine I took off the top and the plastic ring and just play with my xbox completely open.

Hope that helps

Ok I'll try that and get back to you thanks : )

ok I just tried it and it just sayd open tray still, how long should i knock on it till?

your disk reader is broken thats it