Ath0 adhoc Dosen't Work

Hi there,
I have running the last current version of 5.1 and the last Atheros driver, I can make work the cards on Hostap, mode 11a, 11b, 11g, etc.. but I have no connection at all on adhoc, in any mode.
someone knows is this a problem with the driver or is a special setup to make it work on adhoc mode to build a p2p connection?
some times when I run "wicontrol -i ath0 -l" I can see the other station connected but is only for a sec. and gone again, same thing with both ends

my settings are:
ifconfig ath0 172.16.20.3 netmask 255.255.255.0  ssid atheros media autoselect mode 11b mediaopt adhoc


thanks