Autoblog keeps importing the same posts from a particular blog

Hi,

Autoblog keeps importing the same posts from a particular blog in my network. Those posts were already imported to my main site, but I got the same posts imported over and over every day, and I have to delete all the duplicated posts one by one. All the setting for this blog is no different than the others. What can I do to fix it?

Autoblog plugin has been giving me headaches. I just posted another issue regarding featured image in a separate question.

Thanks,
Anais