Right, one it's reloaded there's not much that can be collected to determine what happened. The "show version" command of the PIX lacks the reload reason, unlike the "show version" command of IOS.
One thing that I would suggest the original poster to try the "show crashinfo" command - if the PIX reloaded because of a software bug there is a chance a crashinfo file will exist, and the information in that file can be used to determine if the problem is caused by an existing bug (for which there may be a version with the fix) or by a new bug that requires further Cisco engagement.
By the way, the "show crashinfo" command was introduced in PIX software version 6.3(1). If the software version is < 6.3.x then the crash info is just dumped to the serial console. If there is no terminal connected to the serial console then this information is lost.
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...