"Please cancel this upload, refresh your browser, and try uploading the file again. If this problem persists, click the help tab."

This error is caused due to an interruption in your internet connection while you are uploading your file. In order for your upload to be successful, you must have a stable/consistent internet connection. If your internet connection is interrupted in any way while you are uploading a file, even for a brief moment, your upload will not be successful. This will cause the message that you have seen.

One of the ways your computer can become disconnected from the internet during your upload is if your computer goes into sleep or hibernate mode. Many computers have a power saving setting that disconnects you from the internet when the computer goes into one of these modes. This will cause the error message and your upload will fail.

The rate at which your upload occurs is dependent upon the speed of your internet connection. That said, large files will take some time to upload. It may be helpful for you to reduce the file size. One way to do that is using a video converter. I would recommend "Freemake Video Converter" at http://www.freemake.com/ or "Handbrake" at http://handbrake.fr/ -- they are both free of charge and will allow your upload to occur more quickly.

Regardless of whether or not you reduce the file size, please make sure that you do not become disconnected from the internet when you are uploading your audition/application files.