Anyone had any joy setting up IPSec VPN on Smoothwall Guardian with a client such as Shrew VPN. I've got the L2TP to work but the performance is a bit ropey so thought I'd try plain IPSec. However I cant get the client to connect, I'm constantly getting an "Invalid Message from Gateway" during the initial ISAKMP exchange. All setting are as per Smoothwall help files.

Help would be greatly appreciated.