New owners of Epson's Stylus Photo R2400 may not be aware that there are two types of black ink available for this printer: Matte and Photo. If you have the Matte ink cartridge installed, you will not have access to the Glossy paper choices (because Matte ink on glossy paper would not produce a quality print).
However, there is more madness to this method than you might expect. There's also a bug in the Epson driver software (for Tiger, at least) that prevents the printer from communicating the change in the cartridge back to the driver so, even though you have the correct ink installed, the Glossy paper options are still unavailable to choose.
The solution is to launch the Epson Printer Utility, click the Ink Levels button to show the eight cartridges and their respective ink levels, and then click on the black ink cartridge, so that it displays its information in the window. You'll note that it will show the correct information for that cartridge. When you quit the Printer Utility, calling up the Print dialog will now permit you to choose the Glossy paper.
(I'll note that both parts of this hint came from a number of Google searches to rectify the problem for a client.)
Mac OS X Hints
http://hints.macworld.com/article.php?story=20070412101844165