If you are having problem when downloading Flash Player 10.3 and it stops at 12% and timeout in about 10 seconds, then you are not alone. I do not know the exact reason, but it could be related to the redirected download link to *.macromedia.com when you actually trace the logs. In any case, the temporary solution is to download the full installer and run it directly instead of going through their downloader.
Grab the full installation at:
However, if your downloader is still having issue downloading from the above link, it could be that somehow *.macromedia.com actually does not work for you at all. In this case, I had created the backup links below.
For Internet Explorer
For plugins browsers (anything else besides IE):
However, I strongly suggest you do not use the above link unless the latest is still v10.3.183.5 because you could end up not using the latest version and you know how bad Adobe Flash Player is when it comes to security.
Hope this helps you. If it does, do leave me a comment so that I know.