Try reversing the leads on the phone jack, and make sure your preferences are set to pulse.
try the pulse thing first. much of the time these two shouldnt matter, but it can make a difference.
my 522 frequently nags me to connect phone line, but when I check it says no dial outs scheduled and passes the ophone line test.
any chance your house is wired with FLAT cable? That can cause all sorts of trouble with big line losses.
as a final test try plugging your box DIRECTLY into the interface on your house, with and without the dsl filter, then see if it passes phone line test.
theres a slight chance its your dsl providers trouble, to rule that out take your box to a friend, and try phone line test there.
you can see from my comments, I have troubleshooted all sorts of wierd phone problems.
myself I prefer the NID DSL filter splitter installed where the line enters the home, it elminates the need of filters on the individual phones, and boosts dsl speed
please let me know if you find the problem. best of luck, it can be a bear.
oh yeah look around your home, when the phone company installed the interface on the outside of your home they should of removed the interior grounding block. sometimes they didnt bother, or couldnt get inside.
the old grounding blocks dont really like dsl and cause all sorts of wierd issues.