No VPN connect

We have installed the Avast SBS antivirus and it works well except I tried to make a VPN connect and the first time it allowed it for a few minutes, then disconnected me. I try to reconnect and it stops at “Verifying username and password” and timesout with the message “Error 806: A connection between your computer and the VPN server has been established. But the VPN connection cannot be completed…” The second message is “Error 732: Your computer and and the remote computer could not agree on PPP control protocol”.

Before I added Avast it all worked fine.