Here's a thought (I'm sorry I didn't go over the whole problem properly), previously there were bugs in PIX/ASA under which modifying nat 0 access-lists didn't work. Note that this is 8.0.3 we're talking about.
Can you please try the workaround for this one? Remove nat 0 statements and add them back 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...