Well, I suggest not to use any HTML editing software like FrontPage and DreamWeaver either. Yeah, they do have the ability to upload pages as well but ... I would use specialized software for uploading files like WS_FTP and so on. You can get them free online. Just Google and there they are.
But still you have prob.? Check if you have any AntiVirus or Firewall running on your system. If you do, try closing(disable) them for a while. Also, the size of files you are trying to upload to the amount of net speed you have also determine the FTP success rate.