I don't know of any offhand, but perhaps do a search of software that will manage the type of VPN connection you're trying to make in Vista?
Do you mean PPTP? What is the host of the VPN, a Windows Server? Is the Windows Server at the latest patch level? Is it 2003 or 2008? Is Vista at the latest patch level? Do you have the latest NIC drivers for your Vista machine? How about BIOS for the motherboard?