ASA image version is an interesting possibility. What version of ASA image are you running and what version of ASDM are you trying to load?
I would also repeat the question I raised with the original poster - is it possible that there was some problem when you downloaded the image to your server? It might be worth the effort to download a new copy from Cisco and try that image again.
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...