Can't connect to FVS318N L2TP VPN with Windows client - Error 789_case # 25689768

I have a FVS318N that has been in place for a couple of years.  Recently I was asked by a couple of employees to enable VPN access.  So I figured I would play with it and see what my options were/are.  I have applied the latest firmware, 4.3.3-5.

 

I then followed this KB

 

http://kb.netgear.com/app/answers/detail/a_id/24393/~/configuring-an-l2tp-vpn-tunnel-to-prosafe%2Fprosecure-routers

 

All seemed pretty straight forward.  However, when I try to connect from a windows client:  I've tried Windows 7x64, 32, Windows Server 2008r2, even Windows XP, I get an error 789.  I get the supremely generic Event ID 20227 in the windows event log.

 

It feels like I have missed a config step on the Netgear, need to allow traffic in somehow or something.

 

Ideas?

 

Thanks,

Dan