CP-2W unable to talk to sonicwall router

[Andrew McKenzie_2]

I am unable to connect via my CP-2W ADSL router to anything on the other side of a sonicwall router at work, ie ping to sonicwall works, but ports 25, 110, 3389 and VPN through sonicwall all do not work. Prior to sonicwall going in, all worked ok. It is also specific issue to CP-2W as I can get the connections to work by replacing the CP-2w with any other ADSL router that I can lay my hands on (3 so far, Stallion Netgear and DLink).

If there is an easy answer love to hear it. Would also love to play with the MTU etc on the CP-2W, but there appears to be no other access to the CP-2W except for the fairly basic settings that appear in Web Interface????