XR500 VOIP registration problem

I have an xr500 and an allwork 9204 VOIP phone from work that I can use to work from home.  When I attempt to set up my phone it fails the registration process.  This seems to be a problem with the router as I am able to hook the phone up directly to my modem and it works fine.  I set up a static IP for the phone and put it in a DMZ.  I also disabled SIP ALG but it still does the same thing.  The phone did detect that it needed an update and applied that so it seems to have partial connectivity through the router.