This is the newest driver from http://madwifi-project.org/ for atheros chipsets. It DOES NOT SUPPORT INJECTION on older kernels. Starting with 126.96.36.199+ and 188.8.131.52+, injection success has been reported (Forum posting).
Having said that it does not support injection on older kernels, there is an untested patch to allow for injection:
Please post your experiences to the forum.