Hi I think I've found a bug... It looks like when you add a new sip trunk, if you specify a duplicate number, it only checks the port identification field and not the authentication id field. Basically, I create a new sip trunk, typed a number and it went to the next page, but then I got an error saying "An exception occurred EditVoipProvider Error: Object reference not set to an instance of an object". and it repeated this error if I selected the VOIP provider. If I change the port identification to match the authentication id, this does not occur as I get a friendly error telling me that I can't have a duplicate number. FYI... I was trying to add two sip providers in a cluster by their actual IP instead of the cluster ip... so the same number can come from both machines... Guess I can't do it this way!