iMovie will only import files that it can edit. You can think of an MOV file as a container. The MOV container can contain a large number of Codecs. If iMovie can edit the audio and video codecs in the MOV container, it will probably import. iMovie also balks at Text tracks, closed caption tracks, tween tracks, and chapter tracks (although iMovie 11 is more forgiving on these than some of the earlier versions were.)
To help you further, see if your MOV file will open in QuickTime Player. (If it will not open in QuickTIme, then iMovie will not handle it either.)
In QuickTime Player, type the letter i while holding down the Command Key. This should open the QuickTime Inspector. Tell us the dimensions of the movie and everything you see listed next to the word FORMAT.
hello, it is true that not all .mov files can be imported to iMovie due to different kinds of codecs it contains. for those cannot be opened in iMovie, you can try to convert them to iMovie supported format with Video Mate. there is a "iMovie" column in it to make sure the converted file is iMovie type. Good luck!