Hi, this is my first posting here and I'm writing in despair because my new network-enabled Brother HL-2070N printer does not seem to be reachable through AirPort. I have a wireless router to which a Windows XP desktop is attached using a LAN cable. My Apple PowerBook G4 uses the wireless capability of the router through AirPort. I installed the printer by hooking it up with a network cable to the router and following all the manufacturer's recommendations. All drivers installed etc. I set up an IP address for the printer and Windows has no trouble printing to it, but the printer is totally invisible to the Mac when I use AirPort. When I plug the Mac into the router using an Ethernet cable - voila - the printer pops up automatically in the Printer Setup menu and I'm able to print to it. I called Apple support and they had no solution to the problem, basically they could not tell me why this was happening and didn't think it should be happening.
If anyone has encountered a similar problem and has found a solution, please HELP

I have the same problem now (a year later): Mac hooked up on routher through ethernet cable no problem, Mac connected through AirPort: no printer. (The server browser does see the printers IP though...) No solution yet, will look further into it...

try updating the router firmware. Go to the router manufacturer's web site to download the latest firmware. I did that and it solved the problem. Now I can print to the networked printer from my Mac, which uses AirPort to connect to the router.