After digging a little further, the FreeBSD 8.2 man pages on ath() mention the AR5005VL specifically as not supported, so it's possible the AR5007G would similarly be unsupported assuming the chipset number indicates it's a derivative. As far as I can tell, AR5007G support is through a separate driver in Linux, so it could very well be the case. Just in case anyone else has this same thought/problem ;)
It was just a card I had lying around and (incorrectly) assumed would work. No big deal. Thanks for the response :)