It appears that the MSM failed over due to a process crash. The process that crashed was snmpmaster process. It appears that the backup MSM was not in synch with the master which would have caused an outage as the hitless failover could not take place if the backup MSM was not in synch.
I plan to take some actions to prevent this happening again around on May 31 around 4:30pm-6:00pm . Also the firmware upgrade will be applied as well. The switch may require to reboot and it should take less than 10 mins during that time you might experience the intermittent issue. The extra time is scheduled for if there is an unexpected occurrence.
Resolved as of 2011-05-31 17:10:00