This problem has been ongoing for several versions of OS X and the last five printers I've had and I'm finally over messing with it. For some reson, when using a wireless printer with OS X this is a repetetive problem, and I think if I configured the printer to a static IP address instead of using DHCP, it might work better. At least once a week, if not more often, I'll print something and get the ubiquitous Dock error of "Printer is not connected". The printer is still in Preferences, but if I delete it, then it doesn't show up as it should for selection.
The only way to fix this is reboot, and then the printer shows up again in Preferences. I select it and all is well again...until a few days pass and the same thing happens again. Using an HP LaserJet P1102w, still a current model, but it doesn't matter which printer I use. I also have an Epson Artisan 725 and the same thing happens with it about once a week. Also, this happens from both my Mac and my wife's Mac, so it's not an issue with just my machine.
I've searched for documentation on how to setup a static IP address for a wireless printer with the Airport Extreme, but all I find are tutorials on how to do it with an ethernet hard-wired printer. Any help would be greatly appreciated.