FCPX crash on file import

I installed some free audio plugins, after which FCPX started to crash when trying to import material. Doesn't matter; drag and drop, Import button or from the pull-down. My system also crashes com.apple.Audio.Infohelper, which I can't seem to locate (or trash).

I first removed the plugins, but today I went back to a 4th of august TimeMachine copy. The problem turns out to be still there, leaving me clueless.

Thanks for any help!