We are experiencing similar issues in our environment. I have been updating all of our HP BL460 G8 blades to ESXi 5.1 U1 and in the process also updating the Management Bundle to 1.4.5-3. How I noticed a problem was we were getting constant entries of failures in the event log of the hosts. Message is "Cannot login user @127.0.0.1:no permission" This is with lockdown mode enabled. If I disabled lockdown mode then I still get entries in the log for log in and log out every minute or so. This is very annoying for troubleshooting purposes and needless to say is going to cause our vCenter DB to grow.
Does any one know of any updates to this issue? I have already updated six of our 40 + hosts and all six have this issue.