Not sure if this helps, but when I run Firefox from the terminal I get the following errors before Firefox opens.
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/share/ubuntu/unity-webapps/userscripts: Error opening directory '/usr/share/ubuntu/unity-webapps/userscripts': No such file or directory
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/share/gnome/unity-webapps/userscripts: Error opening directory '/usr/share/gnome/unity-webapps/userscripts': No such file or directory
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/local/share/unity-webapps/userscripts: Error opening directory '/usr/local/share/unity-webapps/userscripts': No such file or directory
Not sure if this helps, but when I run Firefox from the terminal I get the following errors before Firefox opens.
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/share/ ubuntu/ unity-webapps/ userscripts: Error opening directory '/usr/share/ ubuntu/ unity-webapps/ userscripts' : No such file or directory
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/share/ gnome/unity- webapps/ userscripts: Error opening directory '/usr/share/ gnome/unity- webapps/ userscripts' : No such file or directory
** (firefox:5823): WARNING **: Failed to open webapp application path dir /usr/local/ share/unity- webapps/ userscripts: Error opening directory '/usr/local/ share/unity- webapps/ userscripts' : No such file or directory
(firefox:5823): Gdk-CRITICAL **: IA__gdk_ error_trap_ pop: assertion `gdk_error_traps != NULL' failed