VPN Dropping Connections Every Few Minutes

I'm having a problem with our Windows 2003 Server VPN server in that it
regularly drops connections every minute or so. Unfortunately, I'm not
seeing anything in either the server's or client's event logs that is
indicating an error. I have also noticed that while connected, the client
machine uses the parent connection's DNS servers and not the DNS servers
provided via the VPN server. Perhaps this is related. So my questions are:

1. How do I go about figuring out why the client connection is being reset
every minute (almost like clockwork)?
2. How do I force our client machines to use the DNS servers handed out by
the VPN server?

Any and all assistance is appreciated.

Thanks.