After doing a clean install of Ubuntu 12.04 I realized the sound was missing as I played a YT video but couldn't hear a thing. I managed to troubleshoot that problem, got the sound working, then installed Cinnamon and a few applications from the Ubuntu Software Center then went back to play a video on YT but it crashed and has been ever since. I tried installing, re-installing the Adobe Flash Player, from the Ubuntu Software Centre, from their website but so far the problem persists.
Solution lies slightly away from package management. Adobe ships new version compiled with sse2 flag, so it is now defunct on older computers (like mine Sempron 2400+) Problem is solved by replacing libflashplayer.so by hand.
mkdir /tmp/install_flash cd /tmp/install_flash/ wget http://engels.manf.nl/archive/flash/flashplayer11_1r102_63_linux.i386.tar.gz tar -xvzf flashplayer11_1r102_63_linux.i386.tar.gz sudo cp libflashplayer.so /usr/lib/adobe-flashplugin/
Also, you can download plugin from official site from 'archive' section.
I also had Flash Player problems after a clean 12.04 install on my brand new Intel Core i7 system (running 32-bit i386 Ubuntu), and tried re-installing the Flash player (several times).
One thing I found (with the help of the previous answer) was that the
libflashplayer.so hadn't been installed at all.
It appears that the
flashplugin-installer package (which is what I used) didn't actually install the flash player.
adobe-flashplugin package does install
libflashplayer.so, however that didn't seem to fix the problem.
I then tried the fix described above... that also didn't help.
gtk package s also didn't shed any light.
Hope this helps somebody.