Go to
http://whatismyip.com on one of the PC's on your internal network, and check it's the same one as is resolving to your DDNS name.
Just because the ping is coming back ok and the name is resolving back just means that the IP address DynDNS has stored is live, it doesn't tell you whether or not it's still
your ip address.
Edit: Read your posts again and it seems that you may have done some of this already. BTW, I have a similar setup to you, VPN, SSH, RDP and a few other bits still work.