So your still using the old swap disc trick method, sorry dude, the only advice i can give you is do yourself a favour and get the latest mod chip installed (eg/ Messiah 2). I can assure you you wont be having these sort of problems.. seems like its definitely your chip not recognising the disc. You can try on another media, DVD-RW or CD-RW, to save u wasted discs if it doesnt work
Good luck.