It happened to me only once in the 5x abyss. I was kitting a room as usual to reach lv52, and i founded a fighter and a cleric in one of the halls..Suddenly and without reason, he started attacking me and the cleric was,obviusly healing him..I managed to run out of the pvp area as i had a lot of t3 pots and stones and i was all scroll up..
Things are much better on lv6x abyss right now, a lot of mature ppl willing to make a pt ^^