No Genius Results for Recent Purchases

For the past several months I have had issues with Genius where all recently purchased music from the iTunes store is unavailable in my Genius mixes. Looking through my purchased music I have noticed that all music purchased before 4/15/10 has genius results but all my music purchased after does not. I am also assuming that the issue is not based on a lack of similar songs as the Black Keys Attack and Release album has results but Brothers (purchased after 4/15/10) does not. I have turned genius on and off, updated iTunes, and updated my genius results, all to no avail. Anyone have any ideas what might be causing this problem?

Thanks,

Sig