>>Hi,
>>
>>Since two days ago I have been having a problem connecting to a customer network via Windows VPN. I get error:
>>

>>Error 800. The remote connection was not made because the attempted VPN tunnels failed.  The VPN server might be 
>>unreachable. If this connection is attempting to use an L2TP/IPsec tunnel, the security parameters required for IPsec negotiation
>>might not be configured properly
>>

>>
>>When I shutdown (for 10 min) Avast AV/FW, I can connect, however. I called Avast support but the support person says that Avast does not usually block VPN connections.
>>
>>Is there a log that will show me what is blocking this VPN connection?
>>
>>TIA
>
>It's Avast - there are several features of Avast & one of them is 'web shield' or something like that - supposed to be protection from phising sites and block some mailware - anyway try turning that feature off.

It is not Web Shield but Firewall of Avast that blocks it. I just tried, first, by setting Web Shield Off for 10 minutes. Nothing. Then when I set the Firewall Off for 10 minutes, I was able to connect VPN.
Strange thing though is that it used to (prior to a few days ago) never stop me from VPN connection.