Trash FCP X Preference

I have a question that I hope you could help me.
In FCP X 10.0.8 if I delete my preference the background render is check, show reference waveforms is check, copy files to Final Cut Pro Event folder is check, filmstrip view is the default and many other but in version 10.0.9 when I delete the preference is different.
Do the default preference change in FCP X 10.0.9.

I am having problem in FCP X, I can't turn on audio skimming is always off, Can't uncheck A/V Output.

There was an OS change that effected this.

Run this string in Terminal

defaults delete com.apple.FinalCut

I'd also always use Digital Rebellion's free app "Preference Manager" to delete pref files. Fast, safe.

Yes I use "Preference Manager" all the time I also have Digital Rebellion Pro Maintenance Tools. But I still having a problem in FCP X, I can't turn on audio skimming is always off and I can't uncheck A/V Output.

Try just reinstalling the app. Move it to the trash, go to your App Store "Purchases" tab, and you can install it again. Won't mess anything up. Once you're up and running, empty the trash.