We had this issue also. We removed the default SNMP communities from all switches (not knowing if that was the actual problem, but we discovered that some switches did not have their default communities removed while investigating).
Unfortunately, this does not show up in the configuration one way or the other. You can "show management", but I'm not sure at the moment to see what the actual community strings are that are defined.
configure snmp delete community readonly all configure snmp delete community readwrite all configure snmp add community readonly yourcommunitystringWe have not had the problem so far, since doing this.
We are a bit annoyed that the switches ship with these enabled, and they DON"T show up in the configuration.
