airport extreme with linksys wrt54gs

[bash54]

I'm having trouble getting my G5 powermac to locate my wireless network. I just installed an airport extreme card and the airport 4.2 software, but airport cannot find the network (there's no security, passwords, etc). I have a powerbook G4 setup right next to the G5, and it finds my network with no problems. I have both a wrt54gs wireless router and a wre54g extender, and the laptop detects both of them, but no luck with either on the desktop. Any suggestions as to how I can get the network recognized via airport? Is there any chance the airport extreme card (which is plugged into the built-in antenna) has worse reception than the powerbook's airport card? I'm running 10.3 on the powerbook and 10.4 on the powermac, but this shouldn't matter...Thanks for any help!