As I have said, FCPX has an I/O problem with files in system as the app will hang for 1-2 minutes, moving through problematic code, before going back to the exact same spot ready for the angry editor to do what she wants to do unless one forgets during the "wonderful" delay imposed upon the user during the fetch to another clip or operation within the program. 10.9 did NOT have this problem so, it leads one to say the app, modifiied for Mavericks, now has the problem while the Mavericks OS has worked for me without issue, including full use of the complete Adobe cc app set. As stated before, this is a software bug that has NOTHING to do with the inherent function capability of the program but rather with its frequent inability to efficiently connect to other parts of the app to do an edit or drag a clip onto the timeline as needs warrant. Because I build systems, I know a little bit so, IMHO, this access isue is definitely fixable and should be done so quickly because Apple will take a hit from pros using this specific program, which was updated to highlight the prowess of the Mac Pro, a machine fast enough to cover up the spinning ball issue that plaques users like yours truly who don't have a Mac Pro handy to do the task at hand.