Keyboard Volume-down key is always pressed

Hi,

i have the MB110D Keyboard and i use it with an Macbook Air (yosemite) and thunderbolt display.

Since a few days, always when i plug-in my stuff to the macbook the Volumne-Down key is always pressed. (but it physically is not pressed)

I can see that because of the centered volume popup is always shown.

I have already tried to restart the computer etc. but it doesnt make anything better.

Also some other keys are not set to the function as they should...

Has someone an idea whats going on here?

Thx,

Flowj