Did you wait until the Xbox stops scanning the drive? If you start up boxplorer or any file management app. before the xbox finishes reading the disc and EvoX says "Game" at the upper right hand corner, then you won't be able to read the disc. The file management app will say the drive is empty (unless it has the option to re-scan the drive). Probably not your problem, but I figured I'd make the suggestion.
Otherwise you might find yourself on eBay looking for a broken xbox with a working dvdrom drive.