Shoutbox

I know I live in the United Kingdom and you in Canada, but one of my relatives had an identical problem; and phone exchanges work virtually the same in both countries.

The phone could dial out, but not in. What sparked this problem off is unknown, but it was a problem with the local exchange.
The way to check this problem for sure is to go to the phone connected to the line that is playing up. Then dial your own number, normally this will give you an engaged tone (or busy signal of some sort), however if the phone continues to sound like it's ringing somewhere the problem is with the connection between your phone line and an exchange. Since the exchange will be property of the phone company you should contact them and ask them to repair the problem. It isn't that much of an uncommon problem, happens from time to time.