Someone else can correct me if I'm wrong but I believe that this means you had a high severity event trigger in the last 5 minutes. You should check your events on the sensor when this happens to see what was triggered. The condition should clear on it's own provided you don't have a steady stream of high severity alerts coming in.
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...
[toc:faq]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 and UDP are I...