Please forgive me for starting a new thread but I thought this might be helpful to the various people (using different threads) who've reported installation problems.
I'm running 64-bit Windows7 with the 64-bit version of IE9. After downloading Flash Player version 11.3.300.268 I could not get any videos to play and the Adobe screen that showed the FP version didn't show anything, making it look like it wasn't installed (even though it was based on the Control Panel.) I tried all the Uninstall/Install suggestions people on other threads listed with no luck.
What finally worked for me was "Enabling" the "Shockwave Flash Object" add-on listed under IE9's Tools>Manage Add-Ons menu. I had disabled and, I think, uninstalled Shockwave a few days ago since I was getting constant warnings about questionable content. I don't totally understand the reason for the Shockwave module but since I'm back being able to view videos, I'm not going to care. (I don't see Shockwave in the list of installed programs in the Control Panel.) I would suggest to people to try combinations of downloading Shockwave disabling it under add-ons, uninstalling it, un- then reinstalling FP, and then enabling the add-on, if it's there.
One curious thing I'm seeing - when I open the Windows Control Panel I see "Flash Player (32-bit)" which led me down a number of bad paths, since as I said above, I'm running 64-bit stuff.
Good luck to everybody who can't get this working. I feel for you all because I'spent many hours over the last couple of days trying different combinations of fixes. I'm not much of a techie and I know the above is convoluted, so YMMV.