vpn weired problem

i have 3 DC's and 3 member servers, all working properly. Recentely, the
remote access serivce (VPN) stopped working. I reset up the Routing and
remote access on one of the dc,and 2 additional member servers with the same
results.

The story is like this:
i am trying internally,which means that i do not have to worry about
firewalls and routers. I can not connect from a workstation to the remote
access service for any user who is granted permissions to connect. But, i
can connect with the same user account from any server or member server. no
firewall is enabled at all. If i try to connect from a workstation on the
same network, it just says connecting and that it it, then it quits. on the
same worksation , i go to command prompt, and type netstat -a, and it shows
me that it did established a connection to the remote access server. I tried
everything, remote access policy dhcp relay agent with no luck. i am doing
pptp. nothing special, and i am going with the default when i setup the
routing and remote access server.
Any ideas