If the still images in your project (that you created with the Studio frame grabber, jitter on playback) it is typically caused if there is motion in the frame of video you grabbed for the still.
You can reduce/eliminate this jitter (flicker) by checking the option called "Reduce Flicker" in the Frame Grabber toolbox.
A frame of video is comprised of 2 fields that are interlaced. If the Reduce Flicker option is not selected, Studio grabs both fields of video. If there is lot of motion in the frame, this will cause the two fields to be different, producing flicker.
If the Reduce Flicker option is selected, Studio grabs one field and then doubles it to produce a full frame.
Because only one field is used the "Reduce Flicker" option does reduce the video resolution. Detailed information on how to use this option can be found in the Studio manual.