VPN client connection failure

Sometimes my VPN client couldn't connect to VPN serever, the Windows XP reports error 721
which means VPN server is not responding. But
sometimes it works. Is it the router issue client side?

I set the VPN IP range between local IP 192.168.1.200 - 230. When VPN client is connected, the VPN client IP still carry its
previous setting (192.168.2.xx), is it correct?
From the docs, VPN server should assign a new IP for VP client?