I think that whenever a lot of champions (around 4 or more) get a buff or de-buff at the same time the game crashes. Whenever creep and crawl activates the game crashes, and just now I had elsari coven and the opponent spawned in 4 tasty morsels, the game crashed only when it tried to give them all a de-buff at once.
Player Online counter broken (it says now 333 players online and you can only see 120 players in totaal lobbys and ingame)