I believe at one point, I spoke with a Tier 2 person from AT&T and they said that a possible firmware update would be coming out for the NVG510 sometime around December.  It addresses an issue regarding static IP addresses, and my hope is, a fix for the PPTP VPN issue.

I agree, it exposes the machine to the internet, so a strong firewall is a definite must!

I was ready to throw in the towel with AT&T before getting the workaround to work.  The last time I called them, they said there were over 27 different notes in my account with the issues I had with the modem.  I must have spoken to at least 10 different people on trying to get a resolution, and also contacted Motorola tech support as well.  Whenever I said "VPN" they would respond with "Oh, that's a business related issue, we don't support that", even though it was just me trying to use it for work from home.

What I still don't understand is why the DHCP NVG510 server wouldn't supply me the WAN IP address when I did a IPCONFIG /release and IPCONFIG /renew.  I had to actually power down my computer, and restart it before I got served the WAN address over DHCP.  Any ideas?  Perhaps this is the reason why some people have to MANUALLY assign the WAN address on their machines or alternate routers?