Lost video clips

[ESgt]

In a presentation I'm preparing, I've inserted video clips on three slides using the 'Insert Movie' button (one of the 4 appearing on a slide panel). Tested these by running them in 'Slide Show'. On returning to it the next day the clips and the panels they were on, have disappeared. What can cause this, please? I've tried with mp4 and avi versions of my clips.

[RusselB]

What format were you saving your presentation in?
If it wasn't the Open Document Format (.odp extension) then there is a chance of loss of formatting and/or data.
If you weren't using the Open Document Format, then try again saving the presentation using that format.

[Bidouille]

I've inserted video clips on three slides using the 'Insert Movie' button

This is not a real insertion because video can't be embedded into ODP.