Can anyone tell me of any reason why clients using my Chillispot server are not able to make a vpn connection back to their own offices?

I have installed a chilli server on my corporate network to allow guests to connect to the internet without accessing my corporate LAN.  My config is essentially the out of the box version running on Fedora Core4, with the only difference being that I am using an external FreeRADIUS server.

My wireless clients connect and get a 192.168.182.X IP assignment and allowed to connect to the internet. The are not able to make a vpn connection back to their own networks however.

tia.