AVCHD convertion

Hi Iam having a few problems with my I movie reading avchd files it worked ok from the ad card but from the Panasonic camera hard drive the movie clips show as question marks and won't import . I have plugged the camera in and it shows on the desk top I opened the icon and copies the avchd to a external hard drive but trying to import it it s greyed out is there a free prog that I can download to convert it to a file that I movie 11 can read and also will I have to do it clip by clip so I can edit in iMovie 11