You also have to check that the ADSL-modem is connected to the 1st incoming phone connection. Also if the case that the ADSL-modem and splitter is connected to what you think is the first connection; is it then possible that the incomming connection is splitted up to 2 seperat trails before that ADSL-modem? This is what I have found is the typical problem with people living in a house.Hope that you figure it out.
/Kim