The issue with your code, is that you register events even before your addon loads which can make a lot of unneccessary calls. In this case specially when you would log into combat.
You should do something like:
Lua Code:
local ADDON = ...
local frame = CreateFrame("FRAME")
frame:RegisterEvent("ADDON_LOADED")
frame:SetScript("OnEvent", function(self, event, ...)
if event == "ADDON_LOADED" and ... == ADDON then
self:RegisterEvent("ZONE_CHANGED_NEW_AREA")
self:RegisterEvent("PLAYER_ENTERING_WORLD")
self:RegisterEvent("UPDATE_MOUSEOVER_UNIT")
self:RegisterEvent("COMBAT_LOG_EVENT_UNFILTERED")
elseif event == "COMBAT_LOG_EVENT_UNFILTERED" then
end
end)