Linksys and MS VPN

Recently, i rebooted our Microsoft VPN server. It is a standard setup with
DHCP to allow our users to remotely access the network shares via Cable/DSL.
I have about a 50/50 mix of users that can authenticate. I have google
searched this for two days and am at a loss as to what may have happened.
Any suggestions? The closest i can come up with was the dual addressing that
happens via PPTP. Since you already have the IP of your linksys equipment,
usually, 192.168.1.x and the Internet, usually a routable address, there
seems to be an issue and i cannot figure this out.

I have tried releasing the IP and renewing, ipconfig /flushdns - i am at
the point where i am going to reconfigure the Remote Access. Any help would
be much appreciated.

Thanks