The problem was outlined here http://ubuntuforums.org/showthread.php?t=1725682 but that thread is closed to replies, so my posting a "me too" wasn't possible.
Running the (kinda risky-looking) FireFox add-on called "Flash-Aid" fixed the problem for me -
Once run, I had to go into the Add-Ons page to get to its dialogue box, and it pops up a script in an external terminal window that prompts you for root access, purges the installed Flash Player, downloads the correct version from Adobe, and apparently "does some tweaks".
Worked for me. Thanks to extension author Gonçalves,C.B. (aka lovinglinux) from Brasil, and VinDSL / VanR from UbuntuForums.
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