Media Player Classic / Windows Media Player

I have a number of files that have always played fine in both Media Player Classic and Windows Media Player (although I almost always use Media Player Classic).

I have loaded them on to Xdrive.com, which seems to have worked OK.

But today I downloaded a couple of them back on to my computer from Xdrive.com, and they don't play as well. One of them freezes about a minute into the video; and if you try to scroll the timebar forward, again the footage freezes.

I've been back to the original files which are still on my hard drive and they work fine.

So I guess what I'm asking here is: What might have happened to the files between being uploaded to Xdrive.com and then being downloaded back to my computer to stop them working as well?