Flip Camera Shaky in iMovie?

i have the flip ultra (video camera) and at first when i put my clips in imovie it works, but then after a while of editing like maybe 10 minutes or so the clips will start to shake intensely. i know other people have had this problem too, but some people have the same video camera as me and it works fine in their imovie. i've tried stabilizing to clip motion and it didn't work at all. SOMEONE HELP!!!