I bought a cheap wireless router (an Asus WL-520G) to use with my a TelstraClear cable connection. While it mostly appears to be working fine (I'm using it right now after all) I'm finding a couple of sites are so slow as to be completely unusable. The confirmed culprits are Facebook.com and Last.fm. They don't completely time out but if I get beyond a blank screen it's usually just all the unformatted text down the left side, like the site's style sheet hasn't been parsed or something, and I'm lucky if I see more than one or two images loaded. I thought it was something about authenticated sessions and caching, but forums where I'm logged in seem to be no problem at all, likewise internet banking and other such things go fine.
I'm running XP SP2, using the latest versions of Firefox and (intermittently) Internet Explorer. Both browsers have the same problem. Clearing the browser cache and authenticated sessions in Firefox means I can access either site fine, but only the first time. Everything works fine via a local connection, i.e. plugging in an ethernet cable from the wireless router to my laptop and making sure I'm connecting via that rather than wireless. I've never noticed problems accessing these sites on other wireless connections in the past using this laptop.
I just don't know where to begin with diagnosing this. Any suggestions would be great.