Comment 4 for bug 300741

More of a flash issue. Please disable all your extensions except ubufox and test again, its either flash(best option) or an extension and you have way too many to know what is causing this.
What version of flashplugin-nonfree do you have installed? Is this 32bit or 64bit.
To find out version of flash use the following command
apt-cache policy flashplugin-nonfree