renaming clips

greetings.

i captured several clips from a camera via moviemaker. i
then renamed the clips, organized them the way i wanted
and saved it as a project. the only thing that i didn't
do is save it as a movie as i wanted to go back and add
clips at a later time. today, i opened the project and
noticed that the clips were no visable in the storyline
and that the clips reverted back to their original name
(didn't save the clips the way i renamed them). is there
any reason for this and how do i prevent it from happenin
again?

thanks in advance for your assistance