K-9 Mail message tally doubled

[youngdoc]

I'm running K-9 Mail on my Eris as my main email app. I have it connected to my Yahoo! mail plus account via IMAP. All works generally as expected, except that the new mail icon in the notification bar is always double what it should be, i.e., if I receive one email it notifies me that I have "2" mails. If I receive two, it says "4." What gives?