Since I installed Ubuntu 14.04 I have had a weird problem with the sound-related FN keys - whenever I try to mute, raise or lower the sound using them, the one I just pressed begins to loop for whatever reason, which causes either continuous mute/unmute, sudden max volume or complete mute, respectively. These effects can also stack on top of each other and I have not been able to find a consistent way to stop it other than Ctrl+Alt+F2ing. Also it kind of blocks interactions with the UI, because of something related to the tons of requests to show a notification about the volume status that stack up. I am now in 15.04 and still have this problem, and I must add that all other fn keys work properly. Anyone has any suggestions on what to do?