USB Printer not found

Hi. I hooked up my USB printer, an Epson Stylus CX4200, to the USB port on my Airport Extreme. When I click on the Printers tab in the Airport Utility, the field below "This pane shows USB printers connected to your airport device" is blank. Any ideas? It works fine if I share it from my desktop machine, but I thought it would be nice to hook it up through the router so I could print regardless of whether or not my desktop machine was on. I went to Epson's webpage and downloaded and installed the most current driver for that printer today, so we know that it's as up to date as it can be right now. Thanks in advance for any help!