Keep getting error code 650 but not true

[prha]

Here is my problem.

I have a remote site with 5 pc's that connect to my network over VPN over and ADSL connection. Four of my PC's can connect no problem. One of my PC's does not connect.
The dial up networking settings are definately correct as are the IP settings, the firewall settings etc. I can access the internet no problem. When I try to log on to the network I get through the initial dial up otions until the "veryfying log in" then after a few minutes I get error message "Error code 650 the remote access server is not responding, fail code 0x14"
I know that mt RAS server is ok as all the other PC's at this site and all others can log on with no problems.
I cannot access the PC locally as the Administrator password is not accepted (!!)
I have a feeling that some users have been changing settings but I cannot find why the PC cannot connect to my network when all the remote settings seem to be OK.
Does anyone know what else I can check.

Thankyou

 

[prha]

Forgot to add running NT4 w/s sp6a IE 6 SP1