My Airodump problems.

The first time i tried to boot airodump, it worked great, the shell program launched and the ap's and its packets were all listed. So yesturday i tried to get back in airodump. I do the exact same thing i swear. it doesnt work. The airodump window opens and shows what the columns and rows of where the ap's information would be listed, but no ap's appear. I have tried it on numerous wireless cards and it does the same thing. I do not know what the problem is. help me. Kismet works Great by the way. just not airodump