After recently installing Kubuntu one thing I immediately noticed was the slow performance when surfing the web either via Fire Fox or KDE´s Konqueror web browser.
Apparently it looks as though this could be put down to these browsers compliance with and use of IPv6. This seems to be quite a common problem experienced by many Ubuntu users though there is divided thought on whether this is the actual cause. Though if it wasn´t why does disabling IPv6 make internet connectivity improve to normal speeds?
The work around fix that worked for me was to disable IPv6 in Fire Fox. The thread below discusses this further and explains how to do this.