Thought id share this as i found it to be off some help.
when trying to load my game this evening my 360 whould not read the disk. It just said open tray.
After searching for the fault most off the advice was to open the unit up and clean the lens. I didnt fancy doing this but someone stated that they put a disk cleaner in and it worked.
well it worked for me, and i hope it may help others.