Hi, I know this is a bit of an old post but I figured a simply work around to this problem when I encountered it.
I simply edited my .mkv file to include a underscore after like so .mkv_. Once transferred, I edited the file back to the original .mkv and hey presto it worked. Also after some research on this problem it seems by uninstalling DivX on your PC you are able to transfer .mkv files freely. This didn't work for me but it did for some of the folks over at the xda forums.
The renaming files is a good trick that works for everything that I've tried. I also took "."[periods] out of a few files and they then copied fine. Don't remember if they were .mkv or something else though.