I am having a few issues with FCPX bogging down on my projects. One suggestion that was given to me was to delete FCP and then reinstall. I'm willing to try that but I'm assuming I'll have to also reinstall all of the plug-ins that I have as well.
Just move the application to the trash and redownload it from the App Store. The plugins are not part of the application, or should not be. I’ve heard of one developer who instructs users to open the application bundle and install the plugins there. You shouldn’t do that and shouldn’t use plugins that do.