Try deleting the preferences - I've had some really bizarre bugs recently!
First quit FCPX and then save ~/Library/Preferences/Com.apple.FinalCut.plist and ~/Library/Application Support/Final Cut Pro (Whole folder) to your Desktop.
Then delete both the plist and the folder from their original locations and see if that resolves this issue.
If that doesn't work, look for a file similar to:
/Library/Preferences/ByHost/
com.apple.FinalCut.5609C035-FAD0-53FA-B6DB-3FE3AEF39313.plist
Move that to your desktop and relaunch FCPX.
If that still doesn't help, try going through these steps: [
www.lafcpug.org]
For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]