If you lose connection to the internet whilst connected to a VPN connection on Apple Mac OS X Leopard, then this may help you.

If you connect to a VPN that doesn't use the standard 255.255.255.255 Subnet Mask and having problems in Windows Vista, then this may help.

How to stop OS X from diverting all internet traffic through a connected VPN. If you are having trouble accessing the internet in Tiger this may help.