Sorry, this isn't a solution, but are you using MGCP? I had a problem with a T1 going to a Nortel - not sure what option. The vg200 was using h323 and everything ws working. Over a break I decided to try mgcp and that's when I ran into the situation that you have. I had 2 vg200s, vg200-1 was local PRI and long distance T1, vg200-2 was local PRI and Nortel T1. It seemed inbound calls worked OK, but outbound from the Nortel T1 would lock the channels. IP phones didn't have a problem going out, but they didn't use the Nortel T1. The phone guy and I played with it for a week and gave up. So we're back to H323 and things are working fine.
Mark