When you say they can't talk to each other do you mean that the calls will not set up, no voice, one-way voice, controllers can't even sync?
I am assuming you mean the calls won't set up. Do a CCS trace on each controller and try to make a call. Then post the results here (internal numbers only please). Let us know calling and called parties. Maybe your trunk attributes are set to absorb something they shouldn't.
What does the phone do when you attempt the call?
I may be going the wrong direction with this, but we all fat finger a number every now and then and just simply can't see it when we look back.