I tried searching around but didn't find anyone else who had complained about this specific problem. Sometimes when I download a video it goes fine, but when it it finished, it shows up as having no data (0 kb). Generally when this is going to happen the video will not preview. I've tried exiting and taking a look at the incomplete file and it is fine, the data that is supposed to be there is, and the file will play. Not sure what is going on.