VPN through Proxy Server

Hi All

My problem is to get Shiva VPN Client getting through my ADSL router (Nokia M1122) and establishing connection. I can establish VPN link through direct 56K dial-up connection, but when trying to do the same over the network, through my proxy server and to ADSL router,although typing correctly IP address of the remote server and getting messsage that “secure connection is established”,I also keep getting message “Unable to obtain client IP”, which at my opinion occurs after remote server requests client IP and WINS/DNS info from my computer. Does anyone have idea how should I configure my Proxy Server and/or ADSL router to make Shiva VPN Client work. (I getting my IP address from DHCP server on my LAN.)

Thanks in advance