Cisco Aironet 350 Bridge Radio Down

Hi,

I have two Cisco Aironet 350 Bridges connecting two wired Lan.
I have just updtated the firmware with the full 12.03T june release.
One is configured as an Access Point/Root, and the other one is
Client/Non Root.

I have no signal radio on the Client/Non root side.
Otherwise, i have checked configuration on the 2 sides, and
they are exactly the same.

The error message in the log is :

Protocol Warning : Lost Authentication with parent : PRNT_AUTH_LOST :
Might be caused by a poor radio link. Check for interference on your
Wireless LAN.

The bridges are connected at 2 antennas Cisco Yagi (13,5 dbi) and are
separated
by approximatively 120 meters.

Any idea on what to do ?