i had the same problem, was playing assassins creed and was 15 min into the game when i heard the burrrrrr sound like some vibrations, but the game kept playing and i turned it off right away. didnt start up the box until christmas day i got guitar hero, tried to start it up in front of family and got the same results as you did opening and closing and not able to read any disk. found out that warrenty was out got desparate and even thought of a switch a roo with a refundable new one.
anyways found the problem! theres a magnet that sits on the disk spinner that came off and was not able to grasp game right. just found out now and glued it back in place and now waiting for it to dry, yeah i was like hell yeah problem solved. the tricky part is taking it apart, go to ; http://www.llamma.com/xbox/Repairs/repairs.htm
click on xbox repairs, then disassemble tutorail. didnt use the tool they told me to use well any ways good luck.