Error 03
Display: BOARD MALFUNCTIONING.
Cause: Main board serial number cannot be read out.
dig out your #1 Phillips and unscrew the 4 screws holding the cartridge in, pop the cartridge out and reseat it. does the error go away?
there's a possibility that your +5 voltage is too high and may have burned out something. these boards are VERY voltage sensitive. test this at the yellow (+5) and white pins (ground) on the power connectors on the back. you shouldn't have it any higher than 5.10 or it can damage the game. I've seen these operate with the Capcom I/Os at 5.00 flat. additionally check at the brown (3.3) and white (ground) pins, make sure your 3.3V setting on the power supply is set at 3.30.
if you have an original NAOMI power supply, it may need replacement for this very reason.