I have 2 servers running ISA Server 2004 Std on top of Windows Server 2003. I had a working PPTP site to site VPN connection that linked the two. Now for some reason, the connection has stopped working. One site can connect to the other but both sites won't connect to each other at the same time. If one site is connected and I try to get the other link up, I will get a host unreachable or modem device error message. Can any one suggest what I can look for? I have already tried recreating the site-to-site VPN setup in ISA Server.