I experienced the same bug as Escheton. When a Treant smacked the ground, everyone stopped moving except one little swordsman. The rest of the game is still going, but none of the other characters move.
Two bugs I ran into: You can waste your level up on an already maxed out sword and when I was in 3-3 on level 5/5, I killed the last cactus dude and then the ruby disappeared. I was totally stuck, there wasn't any way out of the level.