Vonage and Double NAT

I have an SM900 (NAT=Diabled) connected to the WAN port of a CheckPoint Network Security Appliance (wireless router, firewall, antispam, antivirus, VPN server)

My LAN devices are connected to the LAN side of the CheckPoint via a Switch.

On the switch I have two VoIP lines

1 - Vonage (DLink VTA-VD) VoIP adapter that works fine.

2 - Vonage (Linksys WRTP54G) VoIP Router.

The 2nd line has always had a high level of noise in the background which I suspected was due to double NAT so I set up a static 1:1 NAT on my CheckPoint for the Linksys WAN port. Works fine now and tells me double NAT will affect Vonage. We had not run into that previously.

So it seems to me
- If you have customers complaining about their Vonage service
- They are using a Vonage VoIP Router
- You are using NAT in the SM

Then the customer should request a standard VoIP adapter, or you might try disabling NAT on the SM and use the Vonage Router.

Anyone else have similar issues?