I'm having exactly the same issue.
Windows8 Both firefox 18.0.2 and explorer installed.
I was prompted to uninstall (after flash was crashing firefox)
Then on trying to reinstall (install_flashplayer11x32_mssa_aih) I was able to download the file. When I ask it to 'open' it doesn't do anything.
I did on one occasion manage to get it to the 'installing' alert window, but then after letting it sit for a good ten minutes, nothing!
I have also tried installing install_flash_player_10_plugin, and tried intalling from the link provided above. Nothing...
It does show up in 'Task Manager' as a background process but all values are 0%.
I am having the exact same issue with uninstalling and reinstalling with Windows 8, firefox and exporer. I used the uninstall tool from Adobe; however when attempting to install the newest version of Flash player, the install would not go past the initial prompt of making changes on the computer.
Finally got flash to install.
1 Internet properties > Manage add-ons
2 Find more toolbars & extentions (down the bottom left)
3 Opens http://www.iegallery.com/PinnedSites > did a search for flash and installed from there
It would appear that I couldn't install anything, not just flash. Tried to install chrome and exactly the same thing happened.
Instillation above resulted in Norton Autofix opening. "Norton 360 Premier Edition has encountered an error Error:3048,3
Norton 360 Premier Edition
Error: 3048, 3
Norton Autofix Results: 1 item(s)
Installation :: Success