I have tried to use VPN for an hour. My Windows XP was keeping to generate VPN 800. I have tried to telnet my VPN server port 1723 and checked my router is enabled for VPN pass-by too. What is the problem? and then I tried to use my laptop. It worked fine. I was thinking there are somethings to block my connection. Finally, I disabled the internet worm protection in my anti-virus. My VPN works again.

WARNING: DISABLE ANY ANTI-VIRUS PROTECTION IS SO DANGER!!!! I DO NOT RECOMMEND YOU DO THAT. My computer is siting in anti-virus protected network and I have backup computers too. Thus, I did that.