maybe when the net failed the games changed their settings to standalone mode.
go over all the settings carefully.
Thanks stj, I had put them both in stand alone mode when network stopped working, so I could keep using them and confirm it was just network issue. I've since put them back to master and slave, slave and master, and every combo of master/slave/stand-alone I could think of, multiple times each. I've gone through the settings and the manual and tried everything I could think of. Yesterday I tried disconnecting the controls/sticks/fire buttons, thinking maybe there's a button kinda stuck and selecting before I get a chance to change the selection to Versus, but that didnt work.
I pulled the PCBs apart, cleaned them, reconnected them and no change. I checked power supply output and it's fine on both cabs.
I guess my next step is to figure out how to check the power supply at the PCB and figure out which components on the PCB are related to the network (the parts transmitting the red light through the optic cables), and see if I see anything there.