VPN Disconnect problems

I am trying to set up a VPN connection, so that I can use a Wirless data card on the road to connect to my home office and use remote desktop to connect to a system and run an application. I’m using Windows XP Home to connect, and Windows XP Pro in the office;the router is a Linksys WRT54G. I can initially connect to the VPN and remote desktop through the connection,but after 10-20 seconds I get disconnected. During that short time it seems as if my internet connection gets disconnected from my laptop. I’m sure there is a simple answer to this, I would appreciate any help.

Thanks