Drivers not working in 10.4.11 would do as a starting point.
That Epson printer is moving into the vintage realm but obviously yours has managed to keep going despite being unsupported by Epson.
Epson only offers drivers for this printer up to, and including, System 9 (Pre OS X)
Try removing the printer from the print list and then going through the Add a Printer routine.
The scanner is still supported but if you have no success with reinstalling the drivers that you have, try connecting the scanner and launching Image Capture. See if you can scan from there.
Alternatively, launch Preview and select File > Import from Scanner.
A few days ago I finally upgraded my iMac G4 (Flatpanel) from 10.4.9 to 10.4.11. I had not printed or scanned anything since then, but today I needed to do both, and they don't work. I think it has something to do with the upgrade because they were working just fine before that.
The printer is an Epson Stylus 777i
The Scanner is an Epson Perfection 640U
What could have changed, and how can I get my Mac and peripherals to work together again?
Thanks in advance for your help.