Madwafi has driver for this chipset, I have a AR5007 and the driver works perfect on a eeePC.
One thing before you install driver, do a /sbin/lsmod and see if you have another "ath_*" module
loading, you must put it in /etc/modprobe.d/blacklist so it won't load,conflict with new driver.
http://madwifi.org/wiki/Compatibility/Atheros