1) Reset the printing system with Printer Setup Repair from Fixamac. Do not immediately restart.
2) Install latest Epson driver package (epson11526.sea.hqx)
4) Open Printer Setup Utility, dismiss dialog offering to Add a new printer (which pops up because there aren't any yet configured) - we'll do it by hand.
5) Click 'Add+' icon, choose 'More printers...' -> Epson USB -> highlight CX4800 (which should be auto-detected and appear in the list).
6) Wonder about why the Page Setup menu below remains greyed out.
7) Click 'Add' to dismiss this window, then click 'Add' in the parent Print Browser window. Printer list should now show CX4800 set as default.
8) Go into iPhoto, choose Page Setup and ensure that the Advanced settings are sensible for paper size etc.
9) Test print on US Letter, then if successful try Paper: 4x6 Sheet Feeder Borderless photo paper, Full Page.
10) Curse Epson/Apple for whichever initial setup or subsequent printing mis-step can cause a mysterious Print Queue 'stop' (I suspect the supplied OS X Epson drivers are flakey - but have no proof.)