one of our client need access to our network through pptpd vpn,our redhat server is configured with pptpd,clients connect our network for accessing the network,but one client which is having Dsl 502T router when creating connection it waits for verifying user name and password and after giving below error

disconnected

Error 619: A connection to the remote computer could not be etsablished, so the port used for this connection was closed.

i had checked his user id and password with another client and he gets connection without any problem, only this client having problem his windows version is windows xp with service pack 2 and having mtnl broadband connection with usb dsl 502t router.i already turned off his firewall and antivirs settings,i had tried all his vpn connection security settings with different protocols like pap,spap,chap but fail.how do i check on my server pptpd logs for any errors and how do i resolve my client problem.

Please give any suggestions.

Regards

satish