Connection problem with atheros wireless lan

Binary package hint: linux-image-2.6.38-8-generic

Installed Ubuntu 11.04Beta (Codename: Natty) a few days ago, everythink works correctly as in Ubuntu 10.10. Except WLAN. WLAN works out of the box, but the transfer rates are extremly slow. On both sides (AP and netbook) are the signal strength about 80% and the given maximum transfer rates are about 120Mbits. The effective transfer is about 20KBytes.
Using Natty on an Samsumg N150 wich has a Atheros chipset.
My wife has also a Samsung netbook with the same chipset but without 802.11n support (only 802.11b + g).
Suggestions: The problem seems to be the "n"-standart.

ProblemType: Bug
DistroRelease: Ubuntu 11.04
Package: linux-image-2.6.38-8-generic 2.6.38-8.42
Regression: Yes
Reproducible: Yes
ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2
Uname: Linux 2.6.38-8-generic i686
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
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: bernd 1529 F.... pulseaudio
CRDA: Error: [Errno 2] Datei oder Verzeichnis nicht gefunden
Card0.Amixer.info:
 Card hw:0 'Intel'/'HDA Intel at 0xf0400000 irq 47'
   Mixer name : 'Realtek ALC269'
   Components : 'HDA:10ec0269,144dc072,00100004'
   Controls : 13
   Simple ctrls : 8
Date: Sun Apr 17 18:04:03 2011
HibernationDevice: RESUME=UUID=1cecfb39-71f9-4882-bfec-ac4d874c0f26
MachineType: SAMSUNG ELECTRONICS CO., LTD. N150
ProcEnviron:
 LANGUAGE=de_DE:en
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.38-8-generic root=UUID=86c0831c-9fa1-4fc4-b669-0f3b2fc67527 ro splash quiet vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-2.6.38-8-generic N/A
 linux-backports-modules-2.6.38-8-generic N/A
 linux-firmware 1.50
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
WifiSyslog:
 Apr 17 17:51:04 Knutschkugel kernel: [ 2307.822628] exe (3339): /proc/3339/oom_adj is deprecated, please use /proc/3339/oom_score_adj instead.
 Apr 17 17:54:56 Knutschkugel NetworkManager[831]: <info> (wlan0): supplicant connection state: completed -> group handshake
 Apr 17 17:54:56 Knutschkugel NetworkManager[831]: <info> (wlan0): supplicant connection state: group handshake -> completed
 Apr 17 18:04:56 Knutschkugel NetworkManager[831]: <info> (wlan0): supplicant connection state: completed -> group handshake
 Apr 17 18:04:56 Knutschkugel NetworkManager[831]: <info> (wlan0): supplicant connection state: group handshake -> completed
dmi.bios.date: 03/27/2010
dmi.bios.vendor: Phoenix Technologies Ltd.
dmi.bios.version: 01KB.M073.20100327.JIP
dmi.board.asset.tag: SAMSUNG
dmi.board.name: N150
dmi.board.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.board.version: Not Applicable
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: SAMSUNG ELECTRONICS CO., LTD.
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnPhoenixTechnologiesLtd.:bvr01KB.M073.20100327.JIP:bd03/27/2010:svnSAMSUNGELECTRONICSCO.,LTD.:pnN150:pvrNotApplicable:rvnSAMSUNGELECTRONICSCO.,LTD.:rnN150:rvrNotApplicable:cvnSAMSUNGELECTRONICSCO.,LTD.:ct10:cvrN/A:
dmi.product.name: N150
dmi.product.version: Not Applicable
dmi.sys.vendor: SAMSUNG ELECTRONICS CO., LTD.