That happened to me too for a while. Did the character attack, go off the screen, and then freeze?
It might have to do with the character's graphic placement in battle. Try changing the battler's formation to something like this:
CODE
[Formation Setup]
# $game_system.battle_formation = Formation ID
# It’s possible to change the formation (Even an event script is possible).
FORM = {
# Formation ID => [[Member 1 x、y], [Member2 x, y],
# [Member 3 x, y], [Member 4 x, y]]
0 => [[460,260], [440, 240], [420, 220], [480, 280]]
}
In lines 11-22 in sideview_formation.
After doing that, I haven't got the error again...(yet).