There is a whole lot of discussion on the hitachi drive issues not booting backup games. Well, I don't think it the laser problem (well unless you screw it up somehow by open the drive up or do the POT TWEAK method) . Here is a links that could help you out alot on making your backup with hitachi drive modded. http://forums.xbox-scene.com/index.php?showtopic=522506http://forums.xbox-scene.com/index.php?showtopic=522875&st=0
Hitachi Drive is really picky on the type of media it want to read and the type of burner you using to burn the backup games. Alot of successful member have use pioneer burn and memorex, verbatim media to burn the backup games and it successful boot.
And my last suggestion to you is there is a lot more post regarding about the issues with hitachi drive not booting backup. Within xbox-scene.com and xboxhacker.com.
This two sites has help me alot about the issues. Hope it would do the same for you