[kismac] airport extreme card?

I am trying to use kismac to see how easy it is to crack my aiport base station from my airport extreme card in my g5 mac tower.
After installing and enabling passive mode, I am unable to check preferences>driver>injection>use as primary device. 

The option is greyed out.

How do enable this option?

thanks
PS-I have rebooted a few times, and this was the first time I could actually get the scanning to work, I previously received error messages (I forgot to write them down)...anyway, scanning seems to work now... 

thanks for any help....

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