Board Thread:Support Requests - Getting Started/@comment-7054833-20130309210105/@comment-3528606-20130325222630

Again, it will be more clear if you follow what Fandyllic said: If the file is very large, you should wait for it to finish pre-uploading
 * What browser and browser version are you using?

If the file is relativity small, then use the better web browser (or reinstall the current web browser)