VPN connection busy error when client connects

Hey all,

I have just set up a VPN server on my XP Pro machine which
is behind a Linksys router (using port forwarding etc). A
single client can connect across the internet to my VPN
but when a second tries to connect, it recives an error
stating that the connection type is already created,
another one is not allowed. I read something somewhere
that XP Pro supports only one incoming VPN connection at a
time. Is this correct? What can I do if I want more than
one connection? Would buying a newer router (like the
netgear one for around $120) that supports multiple VPN
tunnels be my only option?

Thanks for any response,
Mark.