Are you by any chance running the
Shell Script backup? There's an issue with the sudo method of restarting the Zimbra services, that every fix I have tried only makes matters even worse. "zmcontrol start" run at the command line starts everything; same command run under sudo fails to start the "Stats" module.
I've just ignored it because except for that annoying red "X" on the summary page it doesn't affect anything adversely.
Dan