I had this problem initially when I first started subscribing but it was resolved by buying and putting filters in all the telephone lines I have at home. It has started happening again in that when I receive a tel. call I get disconnected and I was wondering if anyone has any ideas why this might be and how to resolve it.
filter/splitters do fail so try a process of elimination. Unplug all your phones, plug in 1 and ring your phone number (use a mobile - as long as you don't answer it won't cost you) - then see if you get a disconnect. Remove that phone and plug another one in to it's socket and try again. If you do get a disconnect, change the filter for that phone and see if it still disconnects. If not, you have your faulty filter.
If that does not help, are you connecting your ADSL modem via a filter/splitter. If not try using one - this has stopped this problem on at least one occation that has been reported here.
Are you certain all your phones, faxes, sky boxes, 56k modems etc are all connected through filters?