I was having a hell of a time getting my Lexmark 4650 installed and working -- the instructions above helped greatly, thanks! -- and then I couldn't for the life of me get it to print wirelessly (I had had no problem doing this when my laptop was still on Windows). The sticking point turned out to be figuring out how to determine the IP address of the printer correctly -- NOT the same thing, it seems, as the IP address of our router. This page at Lexmark (http://support.lexmark.com/index?pag...erlocale=EN_US) helped. It was actually very simple: the printer itself, if you press the right buttons ("Setup," then select "Network Setup" and keep telling it "OK"), prints out a sheet divulging its IP address.
Surely, though, there's got to be an easier way. I wonder if somebody's got a nice app to determine what's connected to your wireless network (and, say, to control the router -- set password protection, etc.).