Try using a different browser, for starts.
If that doesn't work, then try waiting..
If THAT doesn't work, then send the file to someone you know on MSN, or give it to a staff before posting, and tell them your problem and ask them if they would mind doing it.
Ask a friend first though.
Oh, and when you can see the screen it should say something like 'upload file' then choose the file, which is a .zip folder, and then hit begin scan, then copy everything in the long code box and put it on your thread, or just copy and paste the link that it should give you.