DSL, Router, Server help needed

[probear]

Here's the setup:
1 server running SBS4.5 (WinNT4.0, SP6a)
1 Linksys router BEFSR11 (1-port Cable/DSL Router)
1 Hub
DSL Gateway
Need VPN and total network access to the internet

Initially, when using the router's DHCP, everything worked but the VPN
To establish the VPN, turned off the router's DHCP, enabled Forwarding from port 1723 to Server IP, Enabled Server DHCP, changed the router to 192.168.1.2 and the server to 192.168.1.1
This worked fine for about 12 hours, then the network lost internet ability, with the exception of the server.
When accessing the VPN, a WIN98 and Win2000server machine will connect, but cannot see the server or any part of the network. When trying to establish the VPN with WinNT4.0 server (which I used before to do this), I get error 678, no answer.

I'm beginning to think that it might be best to start from scratch but whatever way I do this, I need help.

Perhaps a list of the settings necessary so that I can compare to what I have now.

**Background info. This change was the result of the first DSL carrier going belly up. The first carrier did the NAT, so a router wasn't necessary. I used proxy server and also had the VPN set up and running.