Movie Malfunction

[SynfulSeraph]

I don't really know what's going on.

For some reason a lot of the videos I have been downloading are malfunctioning and I have no idea how to repair this.

The problem is that when I download anything of decent size 50MB+ or what not the video will download entirely. however when I play the video it will only specify that the file is maybe 12 seconds long, or 20 seconds long, or 24 seconds long (it's random I suppose depending on the video size?)

Whatever the case there's no way a 50+MB file is only a matter of seconds long. Then when I click on the video navigation bar and skip forward the video will SKIP forward into entirely different sections. However lets say I skip forward to the 12th second of a 30 second video. It will play that section for ONLY the next 18 seconds and then when it has reached the specified 30 second mark it will cease the file.

Any ideas what this may be? I've had trouble the past hour trying to figure out the problem but I don't even know what to search for so it's been quite difficult. Please help me if you can!