Hi,
B.A.T.M.A.N. advanced 2011.0.0 (compatibility version 12)
ath1 (ad-hoc) as batman-adv-interfaces ath0 (ap), tap0, eth0.1 and bat0 as a bridge
stp is enabled for the bridge.
STP is no solution. Did you try enabling the bridge loop avoidance ? http://www.open-mesh.org/wiki/batman-adv/Bridge-loop-avoidance
You might need to upgrade to a later batman-adv version though.
Regards, Marek