I have had similar issues. Have you tried to follow the uninstallation and reinstallation instructions by Chris Campbell on YouTube "Clean install Flash Player"? That at least helped me installing the programme. However, it obviously does not seem to work in my case, but maybe you have more luck.
"Note: Newer version already installed" (which is not true);
This indicates that you have a newer version (11.8.800.175?) already installed, and you try to install an older version (11.8.800.174?) over it.
What does your Control Panel / Programs & Features say is installed?
Can you see the Flash animation at http://helpx.adobe.com/flash-player/kb/find-version-flash-player.html ?
Thank you very much for the suggestion. I followed the "Clean install
Flash Player" procedure carefully and ... IT WORKED! Thanks again.
Great, I am glad I could help!