There are a lot of sound problem threads but I haven't seen this problem before.

It started last week.

When I plug my headphones in, the LED on my mute button (on keyboard) starts glowing. And I can't hear anything trough my headphones either.
It is as if plugging in my headphones is the same as pressing on the mute button.

When I pull my headphones out, the speakers make a pop sound (the same sound as the mute button makes when you unmute)

This is for both jack-inlets in my pc (HP Pavilion).

Also, the screen freezes while shutting down (the Ubuntu loading screen with the dots).
This problem started at the same time as the headphones. Somewhere previous week.

Anyone an Idea please?

(BTW when I boot in windows, everything is fine, so it probably isn't hardware or something )

Thank you very much!