Buffer FLV Progressive download

As far as I am aware, if you Insert > FLV or F4V, the skin you can apply to the video is not intelligent enough to preload the video for you.  There are no preloading parameters you can set in Captivate for preloading on those video skins.  So if the video is extra large it may take a while to begin playing.

You can also insert video on a slide all by itself via Insert > Slide Video or Video > Insert Slide Video.

If you haven't tried this method before, give it a go.  I'm not sure whether adding video this way means that Captivate's overall project file preloader will see the video as an asset and preload it along with the other components, but at least there is a small Loading message that appears over the video before it begins playing.

By the way, if you add slide video this way, you don't get the option to give it it's own separate playbar and skin like you do when you use the Insert > FLV or F4V menu.  You only get the normal slide playbar, but scrubbing this playbar only stops the video It doesn't allow you to scrub the video footage.