Ubuntu 14.04 LTS - Volume control keys

I've used Ubuntu 14.04 LTS for 3 weeks. My laptop's(Samsung RV510) function keys did work for volume changing until now. Yesterday they suddenly didn't work anymore when I turned on my computer. I still can use my Fn keys to change brightness of monitor for example.

If I open System settings -> Keyboard -> Shortcuts -> Sound and Media: Then Volume down is set to "AudioLowerVolume" and Volume up to "AudioRaiseVolume". These values are same, if I press my Fn key + buttons I want to control the volume, but still can't change the volume with them.

But if I bind F9 and F10 for example, then it works, then I can use these button to control the volume. If I bind Fn+F9 and Fn+F10 then it doesn't work. It means, something is up with my Fn keys.

Tried to google, didn't find answer to my problem. Hope you can help me!

Not sure if this will help too much, but I've found that if you go through the system testing program (I think that's what it's called, anyways it has a thumbnail of a monitor with a green image, just search for it under installed programs) it will sometimes fix things like that. If you want you can just skip all the tests except for the media key tests, but I find that the other tests are still helpful. You can also try googling for changing fn key values, I know a lot of keyboards have the option to reverse the F keys and the funtion buttons, so that for F1 you would need to press Fn + F1 for example, and the media key that would normally require Fn would do it without it. Hope I helped you a little bit at least.