Fisrt of all I'd like to thank whoever will answer to this post. It will be very very useful.
I've installed a new BT Home Hub 3 in my place last month and it was good. We are four in the house with two PC and two MacBook.
After a couple of weeks I've decided to install Ubuntu on my PC and from that moment as soon that I connect to Internert all the outher people start to have problems. For instance a ping from one of the MacBook lose 60% pf the packets and the resposnse time is aroung 150ms.
This is annoying, even because this happens only with their PCs, my Linux PC doesn't have any kind of issue.
One possible reason is if one of your machines has used a static IP that lies in the dynamic IP address range. That way, two machines will end up with the same IP, and you will get the issues you describe.
(I am talking about the IP of each machine on your LAN, probably something like 192.168.1.xxx; not the IP of your entire broadband on the wider internet)