Currently Being ModeratedFeb 15, 2014 8:27 AM (in response to boltandjaelith)
Just because you've worked with mp3's without issue for years, doesn't mean you should work with them. They are not suitable for editing with in fcp. PLAIN and SIMPLE.
How did you delete your fcp preferences? The foolproof way is to use digital rebellion's preference manager.
And here's a user tip with some troubleshooting tips.
Go thru them systematically and post back if you still are having problems.