ws-ftp has two radio buttons and a checkbox on the main screen below the directory/file listings:
O ASCII O Binary [] Auto
ASCII - is for written text files like html, php, etc.
Binary - is for computer generated files, like the movie in your case, or pictures, etc.
When you upload the movie file make sure the Binary radio button is selected (or the Auto option is checked) to ensure that the .mov file is uploaded in the correct format. A binary file uploaded in ASCII format will not work.
I probably haven't explained it very well but I hope that helps.
-BB-