I don't have a network adapter for my printer
Strange problem. Curious as to the other macs, how they are connected and what OS they are using.
You don't need a network adaptor, the 7800 has built in ethernet, and you can run a cable directly between the printer and the computer. The mac should auto sense and thus you don't need to use a crossover cable. (Although USB should work fine- you have tried a different cable?) as well if it works on other computers. It is possible for the USB or the ethernet connection in an epson printer to fail with odd problems like this.
When installing the printer in the printer control center, make sure you use the add printer choice in the pop up menu when you click the plus button, do not select your printer when it shows in the menu (which will often use an apple generic driver). When the next window opens you will see the printer with Bonjour next to it, wait for a minute and you should see the same printer with (IP). While epson somewhere on it's site states you should use the bonjour choice instead of IP, I"ve had problems which have been solved (at the recommendation of Epson support) by using the IP choice. Once you select it, you should see the Epson SPro 11880 driver choice show up in the pop up menu.
when you said you reset the mac's printing system I'm assuming you did a right click in the printer window in the printer dialog box? Did you do an uninstall of everything Epson first? Some have found
my article helpful when doing this process. You may also need to
un-install built in drivers.
