Deconstructing you technical issues is along process. Start by telling us about your Mac and the OS. We're not watching over your shoulder so you'll also need to explain what you mean by "6 out of 30".
There are many FCPX forums and we've been seeing terrible horror stories about the update from 10.2.3. to 10.3 and 10.3.1. I've been watching these threads for weeks and find no clear explanations or commonalities; the issues are all unique. For instance, "not responding", in my case, has been directly related to user access permissions issues on our remote media server. Attempting to launch a library that has permissions problems either causes FCPX to not respond or to crash. That probably does not relate in ay way to your issue yet the error from FCPX is the same.