I have two FWSM's, each in it's own 6500 chassis.
Version FWSM = 3.1.1, Version 6500 IOS: s72033-advipservicesk9_wan-mz.122-18.SXF4.bin
These FWSM's work in active/standby failover, interconnected by state-link and failover vlans.
After issueing the 'multicast-routing' global command the standby unit has become unreachable, where it would normally be reachable by means of the 'sess slot x proc 1' command.
A 'show failover' command on the active unit reports that the standby unit has failed.
When i restart this unit with the 'hw-module mod 1 reset' command it boots and takes over. The former active unit syncs, becomes standby and becomes unreachable in turn (sess slot x proc 1).
After removing the global command 'multicast-routing' all works fine again.
Seems like a bug to me.