MN 700 and Net2Phone

I understand that the MN700 has a firewall built in.
I'm using an HP Notebook ZD7000 with the MN700 and evrything works well
(except for the periodic disconnections!) but I can't make VOIP phone calls
using Net2Phone.
I believe the firewall is blocking whatever port Net2Phone uses.
Can anybody suggest what I could do - also to avoid the disconnects from the
wireless network.
Thanks