if it is a new broadband activation it may take up to 10days to settle in but it does sound like the line isn't up to whatever speed ADSL is being put down it.
If you are able to get into the router setup pages, normally done by typing
http://<your routers ip address> you can normally find the numbers for your Line Attenuation and more important the SNR margin, if your SNR margin is below 6db then your ADSL will more than likely be unstable. It is sometime possible to improve this figure by using a better quality ADSL filter and by making sure the router is pluged into the master socket not an extension but if this doesnt help you may have to ask your ISP to get the line downgraded to a lower speed.