VPN Connectivity problem

Hello.

A staff member wants to access a VPN protected web site in order to download some articles but there is a connectivity problem between our LAN and the protected web site.

Professor gets the following error message while trying to connect after installing the CISCO VPN client:
“Secure VPN connection terminated locally by the client. Reason: Unable to contact the security gateway.”

Everybody is using fake IP addresses inside LAN.

Every gets internet connection via PROXY server PC that is using a REAL IP.

We need around 30 concurrent VPN connections but the internal PCs must have fake IPs.

Any ideas how can I implement a cheap VPN solution in order to avoid buying a firewall device?

Could you provide some cheap VPN product web links that solve this problem?

Thank you in advance.