I have the same problem, first noticed with the Nelly Waxing.mov video (~59MB) where I get 25-31MB then ends.
Using Win7, tried Firefox 25, IE11, Chrome and recently installed Download Manager Free - all same problem.
The issue seems to be the server feed being interrupted and this download is not resumable.
Peanu22 suggested another download manager that he says works. I got the link from the shoutbox as:
https://www.internetdownloadmanager.com/but looking it says TRY for tree, so I didn't try it as I want a free solution and frankly I should not need to do this!
However you might want to try it.