[Bob_Zimmerman]

I'm pretty sure that Check Point explicitly does not do UPnP. I mean, the protocol is the very definition of a security hole. Its entire purpose is to make changes to your network infrastructure with no administrator interaction. That's commonly known as a Very Bad Idea™ when it comes to corporate-level firewall software.

As for the original poster's question, really it depends on how it is that you're connecting through the firewall. The audio and video connections are handled by a sort of peer-to-peer SIP. One problem I've seen is that VPN-1 tends to NAT SIP connections on its own and if your peers don't know about this, it can break the call. You should probably talk with Check Point's technical support and ask them about "early SIP NAT".