I am unable to get either Cisco or PPTP VPN connections working on my Macbook Pro but they all work fine in my Windows XP Virtual Machine.

I run 10.6.4 but it has never worked since I got the machine. I actually upgraded from Leopard to Snow Leopard when I purchased the MBP but I don't know if it was working on Leopard.

Any ideas where I can start? Apple support are not interested in VPN problems.