MM2 audio and Video problems

I'm working with home video with the intention of making DVD's.

I have made one .mpg and it's about 2 hours and 45 minutes long. When load
the thumbnail into the large viewscreen in the upper right hand corner I
hear the audio, but no video is shown. When I double click on the same .mpg
in the storyline section i see a still appear in the large window, but the
image/movie will not play even thought the timne couinter will tick upwards.

Please help

Thanks