I've posted a question regarding this issue a few times over the past several months. Not to belabor the details I thought some of you might be interested in what the cause turned out to be:
802.11b WiFi was the culprit.
Must be that LG's remotes are RF instead of IR. When someone was in the room with a WiFi session going on, randomly the A/C would come on by itself. Without the WiFi it stays off.