Core issue
A similar issue is documented in Cisco bug ID CSCsd64749.
When the PIX Firewall fails over to the standby PIX Firewall, it loses most of the global IP pool configuration lines and all of the address-pool configuration lines in RA tunnel-groups.
Resolution
In order to resolve this issue, upgrade the PIX Firewall to software version 7.2.2.
In order to download the latest version, visit the PIX Software Download Page or open a case using the TAC Service Request Tool.