I found out that it doesn't work with my Nvidia GT430 and propritary driver 384.90.
Bought an AMD RX550 last week, uninstalled the Nvidia driver, removed the Nvidia, AMD card in, boot up 14.04 and the burger menu and everything is working fine again in the browser.
I noticed then that the current amdgpu driver requires >16.04, switched back to Nvidia card, installed 384.90 driver and voilá the menus are behaving like written above again.
I found out that it doesn't work with my Nvidia GT430 and propritary driver 384.90.
Bought an AMD RX550 last week, uninstalled the Nvidia driver, removed the Nvidia, AMD card in, boot up 14.04 and the burger menu and everything is working fine again in the browser.
I noticed then that the current amdgpu driver requires >16.04, switched back to Nvidia card, installed 384.90 driver and voilá the menus are behaving like written above again.