Okay, I have a Dell Inspiron 1501and my brightness and WLAN function keys worked out of the box, volume keys did not, so I used keytouch to set that up.

The issue is - and here is the extremely strange thing - the up and down keys don't work. When I press FN > Up\Down it alters the brightness respectively, however, if I'm browsing a text document or web page, simply pressing up or down to navigate the text, doesn't work.

Same thing for terminal sessions.

Xev reports the keysym as 0xff52, Up and 0xff54 Down, and the left and right keys work just fine - I have no idea how to get my up and down keys to work.