This is just a throwout in case anyone has the same problem with their Nortel BCM50 that I just had. My line monitor went out. That's not good for me, as my business is rolling out an additional national advertising campaign - I have to be able to see how many lines are in use. Our line monitor had worked initially, but then Wham, out of nowhere, it died.
A discussion at a nortel forum, BCM Line Monitor - Lines Don't Appear in Monitor, helped. Hope this helps you!
All I had to do was adjust the gateway my nortel device was using to match the gateway everything else was using. It was so simple, I could have punched myself!