Hi,
When you went to render the movie it may be that some of the settings were set wrong. If you go into File>Export>Movie and then Settings this will open the Render settings menus. Yous hould have a list of 4 items in the left hand box, these being General, Video, Keyframe and Rendering, and Audio. (Forgive me if its slightly different I am using Premiere Pro 2.0).
Now click on Video and towards the bottom right make sure that the box labled "Recompress" is NOT ticked. Basically this stops any recompression that is not needed (ie footage you have not changed with effects or such like).
It may also be worth unticking "Optimise Stills" in the Keyframe and Rendering menu.
Doing these two things should help and will also speed up the render time.
Mark
www.onlinevideosolutions.co.uk