Often this comes about due to a quirky quicktime installation or a corrupted FCP preference.
If the camera captures in iMovie, you know that it is ok and computer and camera can communicate.
If that is the case, try the quicktime reinstall>
Go to /library/receipts and delete any files that say Quicktime followed by a number e.g. Quicktime703.pkg
Go to the Apple quicktime site and download the appropriate version of Quicktime to your hard drive.
Run the Quicktime installer.
Repair Disk Permissions for your System Disk (Disk Utility > Select the system disk > Repair Disk Permissions)
Reboot
Good luck.
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