Files Corrupt Upon Completion

[pinkfloydeffect]

When I download music and videos I can usually preview the files in VLC, etc. They will work all the way up through 99% then when the final file is rendered it is corrupt and my media player either says it can not open the codec or just keeps repeating nothing? The only thing that worked was changing the corrupt file's name, leaving it in my downloads and re-downloading the file but I'm not sure if that works statistically.