I'm experiencing similar problem like you.
In my situation I can't make CISCO PVC2300 to talk to DynDNS through RV120W.
I tried port forwarding, putting it in DMZ zone, but no success and if anyone can help us on this it would be great.
Furthermore I had Linksys E2000 previously and it was working perfect in this scenario.
Maybe I should open another thread, but since problem is very similar I felt free to post here.