Are you getting any errors on the router ? did you do a debug ? If it connects with XP, i dont think there will be any configuration errors on the router.. It might just be a OS support issue on this particular version of the Cisco IOS software.. refer to release notes and see if there are any limitations..
In the mean time I saw this URL.. Might help you setting up VPDN on vista..
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...