I have an Epson Stylus Photo RX500 (an "all-in-one") connected by USB to a Mac G4 running Mac OS 10.3.9. It has been working for many months. Now, when I try to connect to the scanner, I get an error from the Epson application that it "Cannot open TWAIN." The maddening part is, I can see the TWAIN files installed; of course, I have no idea if something is missing or corrupt. I reinstalled the Epson software disk but it didn't solve the problem. I moved the USB to the back USB port (instead of the extension hub). I restarted the computer and the Epson machine. If I assume some TWAIN related software is missing, what would it be, where should it be located? Thanks!