Previous version of the findbugs plugin worked great for me. I updated to Findbugs IDEA 0.9.9 and now get the error shown in the screen shot.
(This is with 9 M1)
I also tried going to Project Structure->Modules->Findbugs-IDEA tab and selected "Override FindBugs-IDEA project settings", that had to affect on its behavior.
Can anyone provide any insight? Do you have to do some configuration before you can use it?