If your wireless connection is really slow in Ubuntu 11.10 (or in Ubuntu 11.04) this fix can help you.
Opena terminal window and type:
gksu gedit /etc/modprobe.d/ath9k.conf
and add this line:
options ath9k nohwcrypt=1
Restart your system and you should be ok.
Please comment to let me know if this solution worked for you!