That will only work if his router supports the loopback feature.
I had this same problem with my hub, and found there are a few ways around it.
With Verlihub, all i had to do was edit the database with my 'alternate ip' (my wan ip). I then just logged into the hub as-per normal using the internal address (192.168.0.x). With PtokaX you can set the IP check per profile. Just disallow PtokaX From checking the Owner Profile's IP (assuming that's the profile your using). You can find this option in Profiles.
Hope this helps
-R