Has it ever worked right? Reinstall print drivers? This is a reach making suggestions to you because I'm on win7 and have printed to my 4900 via USB in CS5 and CS6. All I know is that Epson's drivers are flaky to the point where my "saved" print settings still randomly disappear and I'm forced to recreate them on a regular basis. The 4900 is a wonderful machine, but don't expect Adobe to offer much help beyond "update your drivers and/or talk to Epson".
Thanks for your reply! I guess I'd have to say no, it hasn't ever worked right, because this is a new installation on a new mac mini. PS worked fine to that printer on my old mac G5, but it has yet to work from the mini. Other info: PS on the G5 will even print to that printer as an "attached printer" on the mini! The only thing that won't print to the 4900 is PS running on the mini itself.
Drivers! Epson warned not to use the install disk that came with the printer for Mountain Lion, so I got them online (actually did it several times). That still seems the most likely problem, except that every other app on the mini, including Illustrator CS4 from the same cd as PS, prints fine.
I tried Colorbyte Imageprint, and it can print PS output to the printer, so all is not lost: all is just weird and/or expensive.