Comment 13 for bug 236518

I inadvertently solved this problem while working on another (gksudo - update manager hanging instead of opening the login box).

After I changed the line in the hosts file 127.0.1.1 so the hostname matched the one in /etc/hostname my buttons came back in Firefox.

Don't know if any of this will help, as I am new to Ubuntu linux and not really sure what I am doing at times, but it is worth looking at - it worked for me.