Call Barring

I have call barring on my phone and currently, a Tiscali ADSL connection at
512k.

Just recently, my connection keeps dropping of and my router cant reconnect.
However, when I disable call barring to call the help desk, the router
immediately reconnects.

Returning call barring to active does not disconnect and even if the router
is rebooted, this manages the connection without a problem.

It has not been a problem in the past, as I have had call barring on for
over 10 years, and ADSL for the last three.

Any ideas anyone?