That's because your burned discs are patched, and are patched for an older version LT2 and they won't work if your disc drive is flashed with LT3, and either installing them to the internal hdd or converting them to GOD containers will not work for them. You need to get an unpatched iso image, GOD files or whatever..
Remember, games can be stored on an external hdd as well including god and xbla games. I personally don't think it's wise to keep games or your launch.ini on the internal hdd, I prefer easy access to them.
Bought a used Nerf Mega blaster yesterday, good condition, but only got one single foam dart for it. And it was so chewed up, when I tried to fire it today it ripped the tip clean off and spat the thing out in two pieces.