OK thanks, you have gave me an idea with your answer. Will this work?
I convert all the mp4 files to a different format and then put them in the same location as the mp4 files (with same name, then get rid of mp4). Will that work?
If so, what is the most Vegas friendly video format? i have had a lot of trouble with formats, so i started using mp4 and it was working fine until one random day, this happens.