VPN clients can no longer access internal resources after you install Windows Server 2003 Service Pack 1 on a computer that is running ISA Server 2000 – SBS2003

If you have installed SBS 2003 SP1 to your Premium SBS install, but have chosen NOT to install ISA 2004 as yet, then you may be having VPN issues. I ran across this issue this week in a site that we inherited. Found the answer in an MS KB -http://support.microsoft.com/?kbid=897651

Many thanks to Merv Porter for finding that one for me!