I am using HP Pavilion g4 with ralink rt5390. After I installed the ubuntu 14.04 with 3.19 kernel, the wifi didn`t work and also the wifi disable/enable button didn`t work. Then I remove the "acpi=off" in /etc/default/grub and run "update-grub", and reboot. I don`t why but it really works. And maybe it can help you.
I am using HP Pavilion g4 with ralink rt5390. After I installed the ubuntu 14.04 with 3.19 kernel, the wifi didn`t work and also the wifi disable/enable button didn`t work. Then I remove the "acpi=off" in /etc/default/grub and run "update-grub", and reboot. I don`t why but it really works. And maybe it can help you.