I run a Wi-fi network at the home office. The network is served by a Linksys wireless router that runs on the 802.11b standard. Apple's Airport card also runs 802.11b and when using an iBook with the LinkSys router, everything worked fine. But then I got the new PowerBook 17″ from Apple, which comes with the Airport Extreme card built-in. Airport Extreme uses the latest, greatest, faster, 802.11g standard. New problem though: The connectivity and bandwidth with the Extreme Card was crap. I'd complained about this before here. So finally, today, I searched through the Apple's discussion forums and found others had run into this problem. LinkSys (acquired by Cisco after I bought the router) told some posters in that form that it doesn't do a whole lot to support Macs but provided a workaround for the problem. Basically, it involves telling the router to gear down to transmission speeds of 1-2 Mbps. That's the power of the Internet for you. Got a problem? Someone's bound to have had the same problem and already solved it. The discussion thread with the solution is here.
Here's a handy guide to the LinkSys router admin pages.