What format are your clips, what type of HD raid do you have them on.
There are two live actions when using multiclip, Switch To and Cut To. Switch will give you Program Feed back and place markers as you play and switch the timeline. Once you stop playback everything is gone. This is the way it is designed to be, no idea why anyone would want this, guess it is a practice run. Normally it is set to do this when you hit 1, 2, 3, 4 on the key pad.
Cut To does what most people want, the switching sticks at stop. Normally it is set to the combo Command 1, 2, 3, 4 on the key pad.