I have been making movies for youtube. Everything was fine till today when almost every project i open, that has already been edited on movie maker and is a .wlmp file, has to ''prepare the files''.  Some of the sections are there automatically (without loading), but 90% of them have the loading sign and it takes 10 minutes to fully open, and at the bottom the loading bar appears and says loading 1 out of 10 files and goes through the process. I video opened without this happening. 

Also throughout editing the videos there are randomly caution signs on some of the clips and they are blank until the playing marker gets to the clip or until i click on them, then seemingly randomly certain sections go back to having caution signs, this isnt a big problem but maybe a symptom. 

I have not deleted the source files. 

Also this problem was not apparent before, and is happening after not editing the movies for a few days.

I am saving as a .wlmp file and the file displays as a .wlmp in folder.

I have searched other forums and cant find the answer to the problem. 

Thanks in advance for the problem.