If you want to know where you're losing speed, run tracert

In XP you'd go Start > Run
Type in cmd and click OK.
In the command box that opens, type in tracert theforumsa.co.za (as example - but it could be any domain you're having speed problems with).
You'll then get a list of response times to reach each server you're piped through and can generally identify the problem leg.

ps. For the record this does not work on Vodacom 3g - it times out all the way.