OK... now I see what has happened. They have changed the options between 5.0 and 5.1 for snmp. There was no support for SNMP V3 before now. I could have sworn I was able to set more than 3 targets without any issue before and indeed I can. As far as I know there was no limit to the number of targets I could set (at least it is not apparent in the documentation) in 5.0 and previous versions.
So I have to wonder what happens to an ESX host that gets an upgrade? Will the targets somehow come over? Will one drop? Will the whole configuration be lost? I just double checked the 5.1 release notes and I don't see any mention of this change but it sounds like this has the potential to break or disrupt some aspects of monitoring for many customers.
