Vista Movie Maker timeline problem

I have imported video clips (Panasonic SDR-S10 video camer -SD card) into
Photo Gallery then into Movie Maker. In both cases the video clips have
loaded Ok and playback Ok. However when the video clips are moved from movie
maker clip broad to the Timeline/Storyboard only approx the first third of
each clip is loaded (This happens both when draging the clips or using
auto-format) Thus a collection of clips total running time 30mins only shows
on the Timeline as 10 mins!!
Has anybody come across this problem and found a solution.
--
Stephen