If you are talking about PPTP from behind a PIX, then yes, 6.3.1 fixes this problem with the fixup prot pptp 1723 command
If you are talking about IPSEC/IKE then this will not work if you are doing NAT, no matter which version IOS you are running.
If you provide a little more detail on what vpn technologies you are trying to use, I might be able to help more.
Jeff