Originally Posted by
dtsm
OP's query did not specifically mention using safari as his default browser.
I've had problem in the past, using my G3 iBook - so now I always launch with IE version 4 (yes, the older the better) to get IP, check whatever 'agreement' needs to be signed, and then launch firefox and my email app.
I use airport (not airport express), still running 10.3 on this iBook.
I don't think it has to do with b/g (and probably n) networks, network cards, or with individual CPUs.
(Caveat, I'm not an expert; but...) I think it's that somewhere in the TCP/IP routines OS X and particularly Safari don't like to be involuntarily rerouted by some wifi network's proxies.