Noticed it two or three times when using either Eowyn's Ithilien Garden ability or the Ithilien Forest spellbook power turns all trees on the map Lamedon white or black, the textures just freak out, I haven't tried it on other maps and it's happened a few times with other players who are in the match also.
Map: Lamedon
Factions played: Rohan/Gondor
Crashes: None