libertas: deautentification from AP

[237 Rumjantsev Egor (PROG)]

Hello.
We have an embedded board based on Voipac PXA270 SODIMM module with 
Linux 2.6.34.6.
We use SDIO WiFi modem on Marvell 8686 as wireless interface with 
following firmware version:
libertas: 00:01:36:1f:23:04, fw 9.70.3p36, cap 0x00000303

After connecting to AP i have following output iwconfig:

[root at Tomb /root]#iwconfig
lo        no wireless extensions.

eth0      no wireless extensions.

wlan0     IEEE 802.11b/g  ESSID:"HPG_NETWORK"
           Mode:Managed  Frequency:2.417 GHz  Access Point: 
00:21:29:8A:E3:BE
           Bit Rate=2 Mb/s   Tx-Power=16 dBm
           Retry short limit:8   RTS thr=2347 B   Fragment thr=2346 B
           Encryption key:off
           Power Management:off
           Link Quality=87/100  Signal level=-56 dBm  Noise level=-93 dBm
           Rx invalid nwid:0  Rx invalid crypt:177  Rx invalid frag:0
           Tx excessive retries:1  Invalid misc:1   Missed beacon:0

After about 2-5 minutes modem has lost connection with AP.
Here is debug output:

libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 233 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 206 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 74 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 233 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 206 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 233 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 206 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 233 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 206 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 0 and size 233 bytes
libertas sdio: interrupt: 0x1
libertas sdio: packet of type 3 and size 16 bytes
libertas sdio: packet fragment (16 < 32)
libertas cmd: EVENT: deauthenticated

Is this problem appears because my AP settings wrong or problem is 
somewhere in libertas driver?
I've tried different versions of firmware and it hasn't helped.

Best Regards!

-- 
Rumjantsev Egor