High bandwidth with really slow page loads

I'm having a problem at the moment where intermittently pages seem to load very slowly. Often I'll click a link or type a url and nothing will happen for a few seconds, then when the page does load it takes another few seconds to actually build the page together and load all of the images. Ping has also produced pretty unreliable results: quite often i'll get 100% packet loss pinging various websites (even if the websites themselves actualy load, albeit slowly).

Although a few second page load time isn't exactly 'slow', the reason I feel like there is a problem is that i have reliable 10mb/s bandwidth (speedtest.net very rarely gives me anything significantly less). It seems as though once a download has 'got going' as such, it can move very quickly, but it just seems to take quite a while to work out what it's doing.

Running FF3 on Vista, behind a WRT54G router with DD-WRT.

Any tests I can do to try and narrow down what the problem is? 10 Meg internet isn't really quite the same when page general browsing takes the same amount of time.

Thanks guys

 

Okay, a bit more information, because I have no idea what's going on here.

How is it possible that, right this very second, i'm measuring a solid 9.8mb/s on speedtest.net, and yet youtube videos can scarcely download faster than they play?