I use this keyboard too and I haven't figured out how to get the game itself to take screenshots. I load up an external screenshot utility, like FRAPS, and set the hotkey to Function + Print Screen. Then I can do the FN + Scroll Lock + Print Screen to hide the interface on screenshots.

Here is a free, light weight screenshot tool on download.com if you don't have one

http://download.cnet.com/Screenshot-...-10061032.html