Standard things apply: recap, clean board of any cap juice, check for damaged traces and open vias, tune pots, and then a new laser if everything else fails.
this might be an odd question but is your DUO set up near any other game consoles? If so, move it away from them and see what happens. Also try unplugging any other game consoles from any wall outlets in the general vicinity. Also, are the Discs you are using ones that worked prior? Some of these systems work better with one type of CDR media over another.