airodump-ng loses all stations after 30 mins

[Yuri]

Playing with wireless I tried to use airodump-ng to see what one can get 
out of it.

Command
/usr/local/sbin/airodump-ng -w xx ral0
works fine for ~30 minutes and then loses all stations.
Restarting this command gets it to the state with no stations right away.
But after I do 'ifconfig ral0 down ; ifconfig ral0 up' command works 
again. Until it loses stations in ~30 minutes again and everything repeats.

It seems that ral0 gets into some internal state that prevents 
airodump-ng from picking up packets. And down/up clears it.

But the output of 'ifconfig ral0' doesn't change after down/up:
ral0: 
flags=2a9c3<UP,BROADCAST,RUNNING,NOARP,PROMISC,SIMPLEX,LINK1,MULTICAST,PPROMISC> 
metric 0 mtu 1500
        ether 00:18:f8:2e:40:25
        inet 192.168.168.133 netmask 0xffffff00 broadcast 192.168.168.255
        media: IEEE 802.11 Wireless Ethernet autoselect <monitor> 
(autoselect <monitor>)
        status: associated
        ssid "" channel 5 (2432 Mhz 11g) bssid 00:18:f8:2e:40:25
        authmode OPEN privacy OFF txpower 50 scanvalid 60 bgscan
        bgscanintvl 300 bgscanidle 250 roam:rssi11g 7 roam:rate11g 5
        protmode CTS

My card is recognized as: ral0: <Ralink Technology RT2561S> mem 
0xcffe8000-0xcffeffff irq 17 at device 10.0 on pci0
And I use 7.0-STABLE.

This seems like a bug in the driver. But I am asking here hoping someone 
will have an answer off the top of their head.

Yuri