This is an iPhoto problem. It is, IMHO, one of the worst photo/video programs ever thought up by any company.
I suggest you find your original video files, which won't contain any edits and or adjustment you have made in iPhoto, and copy them to some other folder on your drive that you create and then import them to LR.
Usually iPhoto stores all original image and video files in a folder called Masters buried deep inside the iPhoto Photolibrary package folder. Which makes almost impossible for any normal computer user to get to.
Next time you are in the market for a new computer think long and hard before you drink the Apple Mac Cool-aid.
Never mentioned iPhoto. It is a Lightroom problem. It can't read movies from my iPhone. If you google this you will find many other lightroom users are having the same problem. I'm looking for an answer or work around.
Sorry read "i" and missed the Phone part. Please accept my apology.