I had this same issue with my Mac with OSX Lion. When I first installed the software the scanner worked from preview, I just had to open Preview, select Import From Scanner, and Include Networked Devices, and the Epson would show up. Then this quit working, and I could not find the Epson scanner, although the printer continued to function. My Linux and Windows machines would find the scanner just fine. Then because of something I wanted to do with a Windows machine, I seemed to have corrected the issue with the Mac. I assigned the Epson NX420 a static IP address in the router, by reserving a specific IP address for the Epson's MAC address. Once I did this, the scanner now shows up in Preview as it did before.