After upgrading to Firefox 24, YouTube videos never load

Question

I have Lubuntu 12.04 and Gnash. Up until yesterday (when Upgrade Manager uploaded the latest Firefox to version 24) all was well.
NOW, the page loads, I click on the large "Play" symbol superimposed over the video image, and all I get thereafter is the circling dots loading symbol.
Gnash gets far enough that it creates the "videoplayback__" file for the video, but it is typically only a few kb large (and it cannot be played, naturally).
If there is a workaround/solution, great - if not, please tell me how to get version 23 back (but also let me know when the problem is fixed so I can get the new fixed version)
Thank you.
P.S. To get this question down to an acceptable size, I deleted all the printer-related Troubleshooting Information that for some reason Troubleshooter saw fit to include....
Before I did so, I was told to: "Ensure this value has at most 30,000 characters (it has 47,676)." ("Value" ???)
Version information:
uname -a
Linux scott-Asus-M2N68-AM-Plus 3.2.0-54-generic #82-Ubuntu SMP Tue Sep 10 20:09:12 UTC 2013 i686 athlon i386 GNU/Linux
firefox --version
Mozilla Firefox 24.0
gnash --version
Gnash 0.8.10 (release_0_8_10-21522-2e609a6)
Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
Gnash comes with NO WARRANTY, to the extent permitted by law.
You may redistribute copies of Gnash under the terms of the GNU General
Public License. For more information, see the file named COPYING.
Build options
Renderers: agg cairo
Hardware Acceleration: none
GUI: GTK
Media handlers: gst ffmpeg
Configured with: CFLAGS=-Wall -g -Werror-implicit-function-declaration -O2 CXXFLAGS=-Wall -g -O2 LDFLAGS=-Wl,--no-add-needed --host=i686-linux-gnu --build=i686-linux-gnu --prefix=/usr --sysconfdir=/etc --disable-testsuite --without-swfdec-testsuite --without-ming --disable-dependency-tracking --disable-rpath --enable-cygnal --enable-python --enable-jemalloc --enable-media=gst,ffmpeg --enable-gui=gtk,qt4,dump --enable-renderer=agg,cairo --enable-docbook --enable-extensions=fileio,lirc,mysql --with-npapi-plugindir=/usr/lib/gnash --with-plugins-install=system --enable-shared=yes
CXXFLAGS: -Wall -g -O2 -W -Wall -Wcast-align -Wcast-qual -Wpointer-arith -Wreturn-type -Wnon-virtual-dtor -Wunused -fvisibility-inlines-hidden

Answer 1

YouTube videos freezing up after about 30s
I am contributing the following observations both as information and in an effort to help FF find a fix for what broadly speaking is an on-going problem, but possibly not as some users have suggested specifically with FF or on the other hand with Adobe Flash. Please forgive the length.
After updating FF23.0.1 to FF24.0 and updating Adobe Flash Player from 11.8.* to 11.9.900.117 shortly afterwards I have found that when using my broadband dongle ANY YouTube video I play in FF freezes up after 26-30 seconds although the progress bar continues; if I give it long enough the screen turns green - a first for me - and I receive a message that the Adobe Flash Player has crashed. The SAME effect occurs in Google Chrome using its default Adobe Flash Player, v11.8.* (it recognizes 11.9.900.117, but I have not tried that in Chrome yet).
With Opera v12.16 and v15, however, with and WITHOUT the turbo feature on for slow connections, I have no problem with YouTube videos. In a single test using FF with an ethernet connection YouTube videos played properly. So, superficially, the problem would seem to be related to a slow connection speed with the dongle, although this does not explain the crashing of the Flash Player in FF and Chrome, but not in Opera: I have been using the dongle since December 2009 and have NEVER encountered this issue before. Also, with FF, I tried playing a flash video on another website at various qualities and the video did not freeze up. So, why this problem with YouTube? It might also be added that FF users have been reporting FF/Adobe Flash/YouTube problems for at least a few years and it is unlikely that they were all using broadband dongles. I do have some difficulty playing some Quicktime videos while using my dongle, which may also suggest an internet connection issue; nevertheless, as noted, this does not explain the persistent and unusual crashing of the Flash Player or the green-screen effect or Opera's ability to play YouTube videos.