"VPN Trouble"

Hello, all. I'm having some problems with the RAS server
in 2003. I configured it as a VPN server with only one
NIC card and made the appropriate entries on my router for
it to be accessible. It worked fine for one day and the
next day, it was like it didn't exist anymore. Clients
can't connect to it and when I looked at its settings,
everything looked fine. I did notice when I stop and
restart the RAS server, all 9 ports I have open show up as
the server in DHCP. All 9 addresses will have
server.domain.com. I know that's probably some of the
problem. Does anybody have any ideas on how to keep this
working for more than a day?

Any suggestions would greatly be appreciated. Thank you.