I do not switch between matte and glossy paper often with my Epson R2400 because of the loss of ink. However, recently I did make the switch and put my PK cartridge in after running the ink out of my matte cartridge. Alas, the printer driver on my iMac, using Lion OSX did not give me the choice of Epson’s Luster paper (the glossy paper). The driver did show the PK cartridge as being installed. At first I thought the problem was in Lightroom, where I was trying to print on Exhibition Fiber paper. I fussed with Lightroom for awhile before something clicked and I solved the problem.
What I remembered was that you had to stand on your head while reciting shakespeare and type with your toes in order to have the driver allow you to choose a glossy paper type. Unfortunately, I forgot which order I had to perform this ritual.
So I googled the web again and found this post in the UK from photo-i which provided a much better answer.
The end result is that you should send something to the printer having chosen matte paper. Any file will do. The driver will give you a warning or error showing that you have a PK cartridge installed for glossy paper. If you then go back to the printer settings, voila, the glossy paper choices are back.
Since I don’t like waisting ink, I have not tried the reverse yet with the matte black cartridge, although I assume the same potion recipe will work….