The same here. I'm not sure if the 'nickname setting' is not supported by the wifi card (I use Ralink 2860 on Asus EEE PC 901) or by the kernel driver (as though with the old driver rt2860sta I didn't have this issue, but I don't remember).
But it appears after calling iwconfig wlan1 nick 'nickname' (/etc/rc.d/rc.wireless -> $IWCOMMAND nick $NICKNAME). So with a few # in rc.wireless it would be harmless (???) to avoid this ugliness