Sudden and unexpected RAS problems

[Coban]

I have 3 VPN clients that connect to my server daily. 2 of the clients are
running NT 4.0 and the 3rd client is running Windows 2000.

1 of the NT clients is connecting without issue.

The other NT client and the Windows 2000 client which are at the same
location cannot connect.
Internet access has been verified so that is not an issue... I can ping
what and whoever and I can load internet pages as well.

The NT client is getting a 678 error, stating that there is no answer
The 2000 client gets a 781 encryption error telling me that no vaild
certificate was found.
I do not see any errors logged on my server telling me about failed
validation attempts.
Both clients connect without a problem using THE EXACT SAME PROTOCOLS over a
modem dial-up connection.

Why oh why can't I connect these 2 clients over the internet? They've been
doing this daily for over a year and no settings have been changed.

TIA, Ari

 

[Guest]

Are you using a Certificate Authority to issue
certificates to your VPN clients?

 

[Jeff D]

On the client that is getting the certificate error, is it
hard coded in the client setup to use PPTP, L2TP or auto?
If your server is expecting PPTP connections and the
client is trying to use L2TP, the connection will fail.