Today I logged-in into vSphere Client and stepped into this alert.
According to KB 1033725 this alarm is triggered when IPMI System Event log is full.
So...to resolve this issue click on the host with this alarm and go to Hardware Status tab, you should see something similar to this which states the log archive is full.
Click View -> System Event Log then click Reset event log. Once done alert will disappear from host but to complete the process you have to click Reset sensors button.