It would be interesting to see if this occurs when the unit is secondary - active.
Are the units identical?
Taken from log message information
Error Message %PIX-3-210005: LU allocate connection failed
Explanation Stateful Failover cannot allocate a new connection on the standby unit. This may be caused by little or no RAM memory available within the firewall.
Recommended Action Check the available memory using the show memory command to make sure the PIX Firewall has free memory in the system. If there is no available memory, add more physical memory to the firewall.
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...