Not sure if its related but i have a similar problem after the upgrade from 10.04 to 12.04.
I usually get a freeze when i close tabs in my browser (often with flash elements, Opera) or just opening a link with a flash video.
After a while opera will be responsive again since the plugin are called in a separate process (plugin-wrapper) which crashes and will start again.
Also using x64 system with NVidia 9600GT and Gnome3 (gnome-shell).
Not sure if its related but i have a similar problem after the upgrade from 10.04 to 12.04.
I usually get a freeze when i close tabs in my browser (often with flash elements, Opera) or just opening a link with a flash video.
After a while opera will be responsive again since the plugin are called in a separate process (plugin-wrapper) which crashes and will start again.
Also using x64 system with NVidia 9600GT and Gnome3 (gnome-shell).