I reported this on 21 December 2004. Having spoken to BT and having engineers out the problem still remains. I got so fedup with contacting BT and getting nowhere I gave up and put up with it for the past 6 years. Now its starting to really get on my nerves.
Engineer came out changed the socked and was told to try a different filter as the one I had could be broken. Numerous filters later the problem still exists.