MacBook Pro printing fails with an Epson printer
Have you tried sharing the printer from the G4 box? This could be a case where the older system is running a set of printer drivers which work well with the printer, but the newer system has either those specific drivers removed, or they just don't work correctly.

To do this, on your G4 box, go to System Preferences > Printer, and select the printer you are trying to do. In there, there should be a checkbox that says "Share this Printer". Once you have done that, you should be able to see it in your print dialogs through Bonjour.

See if that helps.