I suggest you go with "Upload" button. I have just checked there seems to be no issue. Do you remember what link you put in on "Post Video"? You must enter XXXXXX! you cant enter something like flash-files.com or flash-files.com/something.php?idd
and later edit link on Post Thread Page. If that happens, your post will have every detail but in thread display page you will have 0 bytes size shown another possible reason could be browser issue or page couldnt be redirect properly either bcoz of cancelation or network error.
