can't open .mov quicktime files

It says a componant is missing but doesn't say which. I am running Quicktime X.

Try using the Finder "Get Info" or VLC to check what compression format was used and then install the "missing" codec(s package).

It says its a quicktime movie,

That is Probably the "Kind:" entry. Anything in an MOV file container is a QuickTime movie.

Where does it say what compression was used?

Try under the "More Info" heading where it says "Codecs:"

under more info it just says when it was last opened.

Then I would move on to the VLC Player which contains its own codec and does not depend on the QT components. It tends to open many files using codecs primarily associated with "Windows" codecs, transport streams, and the like. If it open in that app, look in the "Window > Media Information..." window and see what codecs it says the file contains. If that doesn't work, post a sample file for examination by one of this forums' regular contributors.

I am experiencing the same problem. I recorded video using a high end JVC camera & this was the last thing I expected (Quicktime being unable to open .MOV file!) It seems absurd after being informed by a JVC sales rep that the camera records in QT.

Here's the more info:
Video is 1280 X 720
Codecs: MPEG-2 Video, Linear PCM, Timecode
Color profile: HD (1-1-1)

The weird thing is that I have access to other Imacs where I work and some of the iMacs open the same files while others don't (like the one I have here at home). Any help would be appreciated.

Codecs: MPEG-2 Video, Linear PCM, Timecode

The QT structure embedded in the OS does not natively support MPEG-2 (MPEG or M2V) compressed data. Normally you would need to purchase and install the QT MPEG-2 Playback component. Alternatively, systems having iMovie '08/'09/'11 installed will automatically trascode MPEG-2/AC3 multiplexed content from a camcorder to all I-Frame MPEG-2/Linear PCM elementary streams in an MOV file container during the iMovie import/capture process. These MOV files will only play on a system having the appropriate iMovie "import" component or MPEG-2 Playback component installed.