Trying to push Flash 11 to my domain's Windows 7 machines (which all have IE 9) through GPO was not working, so as a debug step I decided to install it manually and see if perhaps it was a rights thing or whatever.
Turns out that installing it manually doesn't work correctly either. Running the adobe-provided installer results in Flash player 11 showing up in the Programs and Features list, but it does not show up in IE 9's addon manager, even after restarting flash and rebooting the computer. Perhaps not surprisingly, flash content also doesn't work and I get the usual notice from the object tag snippet that Flash recommends folks to use that asks me to install the latest version of flash player.
Not really sure how to debug this. I'm not seeing errors on the install or in the event viewer, and all the online advice I can find tells me to use the add-on manager to unblock the flash object and similiar; none of which can I do since it's not showing up in the add-on manager.