This error occurs when the peer may not acknowledge that the local SAs have been cleared. If a new connection is established from the local router, the two peers can then reestablish successfully. I think you will have to reenter preshare keys manually. Enter these commands:
sysopt connection tcpmss 1300
This error also may appear when there is an attack from outside. Following link may help you
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...