wireless scan: 'ifconfig <iface> scan' hangs often

[Yuri]

I use wireless with this device:
ath0: <Atheros 5212> mem 0xcffe0000-0xcffeffff irq 16 at device 5.0 on pci0
and very often (most of the times) 'ifconfig ath0 scan' hangs.

First time I do scan it usually succeeds but the second and subsequent 
runs of
this command hang in 50+% of cases.

It hangs equally when I am trying to run this command when network is 
associated and running and down.

Is this a bug in driver or what the problem might be?

Yuri