Well, it seems strange if it does it at random trees, but i've never seen something like this before.
If it is in the editor, it cant be anything to do with triggers/lag/map size, i think.
Mabye the map itself has become corrupt in soem way, mabye try re-loading a different map to see if it only one map.
If this happens on different maps you should re-install AoK, IMO - but if this problem is only restrained to this map, i'm stumped ¬_¬
¬_¬ Scuddles: Rhymes with huggles© ¬_¬
"Scud: the man who could even make God feel foolish." - A Banned User
"Anyway, Scud's not mean, it's not in his nature...he is a bit eccentric though!" - Anastasia