Do you have a manual? I have the manual in PDF form, but its about 5 meg. If you're able to PM me an e-mail address that will handle large attachments, I'll send it over.
If you don't, and want to verify the DIP settings are correct here is the info. Most of this doesn't apply to the problem you're having, but you can get into the operator menu and stop the machine from trying to dial out to ITNET. That might eliminate the modem error.
SW51-Dip switches found on the main PCB near the JAMMA connector
Dip 1 (ON) Normal Play (Default)
Dip 1 (OFF) Operator mode
Dip 2 (ON) ALWAYS ON
Dip 3 (ON) ALWAYS ON
Dip 4 (ON) ALWAYS ON
The SW5-Dip switches can be found near the flashing green LED. These are used to adjust monitor resolution.
Dip 1 (OFF) Medium Resolution (DEFAULT)
Dip 1 (ON) Low/Standard Resolution
Dip 2 (OFF) Low Resolution B Adjust (if you have jittery images, switch this)
Dip 2 (ON) Low Resolution A
Dip 3 (ON) ALWAYS ON
Dip 3 (ON) ALWAYS ON