Are you playing the video from the camera? Or are you reading the video from a file?
Doing some research, the consensus seems to be you must upload the video to a file and then you will have steady playback and editing.
If the camera supports SD card, you take the SD card out of the camera, put it in you card reader, copy it to you hard drive.
While reading from a file software makes corrections for frame rate errors . Example: the camera may be running at 59.5 fields per second, but the video card wants exactly 60 fields per second.The correlation is better when reading from a file, the software just speeds up the rate to 60 fps and does do have to add a field.