Often in upgrading the OS, QT or FCP for some odd reason QT will get knocked slightly off kilter. This shows up when you try to log and capture in FCP (and get a device missing message) but the capture works fine in iMovie.
The usual solution it to force a full reinstall of QT.
This is how:
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.
Reboot
Repair Disk Permissions for your System Disk (Disk Utility > Select the system disk > Repair Disk Permissions)
Good luck.
x