VPN Server Problem

[pinguingilo]

dear...
I have Installing and Configure VPN, Using Poptop....But that VPN Can't be connect...the error like this :

Mar  3 11:17:15 vpn pptpd[2336]: MGR: Manager process started
Mar  3 11:17:38 vpn pptpd[2340]: CTRL: Client 192.168.0.134 control connection started
Mar  3 11:17:38 vpn pptpd[2340]: CTRL: Starting call (launching pppd, opening GRE)
Mar  3 11:17:38 vpn pppd[2341]: pppd 2.4.1 started by root, uid 0
Mar  3 11:17:38 vpn pppd[2341]: Using interface ppp0
Mar  3 11:17:38 vpn pppd[2341]: Connect: ppp0 <--> /dev/pts/1
Mar  3 11:17:38 vpn pptpd[2340]: GRE: read error: Protocol not available
Mar  3 11:17:38 vpn pptpd[2340]: CTRL: PTY read or GRE write failed (pty,gre)=(5,6)
Mar  3 11:17:38 vpn pppd[2341]: Modem hangup
Mar  3 11:17:38 vpn pppd[2341]: Connection terminated.
Mar  3 11:17:38 vpn pptpd[2340]: CTRL: Client 192.168.0.134 control connection finished
Mar  3 11:17:38 vpn pppd[2341]: Exit.

What Have With That...

I have Allow port 1723 and port 47, Using Iptables :

iptables -A INPUT -p tcp --dport 1723 -j ACCEPT
iptables -A INPUT -p 47 -j ACCEPT

Help Me....I am using mandrake running on kernel 2.4.8-34.1mdk

[alxgomz]

I already had such error for a similar setup.
I can come from pppd errors (active pppd debug in /etc/ppp/pptp-options) or from the mppe module (is it loaded?)...
Maybe posting your config files would help...