Ath9k driver causes kernel panic and system freeze on Ubuntu 11.10

After I installed Ubuntu 11.10. I tried bridging eth0 and wlan0 with this script:

#####################################
#!/bin/bash

service network-manager stop
ifconfig eth0 0.0.0.0
ifconfig eth0 up

ifconfig wlan0 0.0.0.0
ifconfig wlan0 up

brctl addbr br0
hostapd -dd /etc/hostapd/hostapd.conf > /var/log/hostapd.log &
sleep 5
brctl addif br0 eth0
brctl addif br0 wlan0

ifconfig br0 192.168.1.15 netmask 255.255.255.0
ifconfig br0 up
route add default gw 192.168.1.1

#########################

And it showed up this error:

l2_packet_receive - recvfrom: Network is down
device wlan0 is already a member of a bridge; can't enslave it to bridge br0.

I have used same scripts on earlier Ubuntu versions; but there was no such error.

Apart from that error, after enabling the bridge, the moment another device tried to connect to it, the system freezes. I ran same script by logging to CLI (alt + f5), then when the freeze happens, error message kept on scrolling on screen (so fast that I could not read anything).

I tried loading 2.6.38 kernel, then also the first mentioned errors showed up, but system did not freeze and the bridge (access point mode) worked fine.

---
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
AplayDevices:
 **** List of PLAYBACK Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC269 Analog [ALC269 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
ApportVersion: 1.23-0ubuntu3
Architecture: i386
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: Intel [HDA Intel], device 0: ALC269 Analog [ALC269 Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ashwin 1563 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf7cf8000 irq 45'
   Mixer name : 'Realtek ALC269'
   Components : 'HDA:10ec0269,10438442,00100004'
   Controls : 9
   Simple ctrls : 5
DistroRelease: Ubuntu 11.10
HibernationDevice: RESUME=UUID=d3930f52-5879-4184-ae59-7d0712e31d29
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
MachineType: ASUSTeK Computer INC. 1005PX
Package: linux (not installed)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-11-generic root=UUID=2ddb9538-ee18-40ec-ae85-2f28759a7486 ro quiet splash pcie_aspm=force vt.handoff=7
ProcVersionSignature: Ubuntu 2.6.38-11.50-generic 2.6.38.8
RelatedPackageVersions:
 linux-restricted-modules-2.6.38-11-generic N/A
 linux-backports-modules-2.6.38-11-generic N/A
 linux-firmware 1.60
StagingDrivers: zram
Tags: oneiric running-unity staging
Uname: Linux 2.6.38-11-generic i686
UpgradeStatus: Upgraded to oneiric on 2011-10-15 (4 days ago)
UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
dmi.bios.date: 04/30/2010
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: 0601
dmi.board.asset.tag: To Be Filled By O.E.M.
dmi.board.name: 1001PX
dmi.board.vendor: ASUSTeK Computer INC.
dmi.board.version: x.xx
dmi.chassis.asset.tag: 0x00000000
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK Computer INC.
dmi.chassis.version: x.x
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvr0601:bd04/30/2010:svnASUSTeKComputerINC.:pn1005PX:pvrx.x:rvnASUSTeKComputerINC.:rn1001PX:rvrx.xx:cvnASUSTeKComputerINC.:ct10:cvrx.x:
dmi.product.name: 1005PX
dmi.product.version: x.x
dmi.sys.vendor: ASUSTeK Computer INC.