On Friday 15 January 2016, Thierry de Coulon wrote:
> Hello all,
> This works fine, except that I often loose the function of the "Alt Gr" key
> (for those who only know the US keyboard, Alt Gr is necessary to access a
> bunch of characters we use in non-English languages.
> This is independent from distribution (I had hoped that switching to Jessie
> and 14.0.2 would help, but not).
>
> What I don't know is what is causing the problem. The rest of the keyboard
> layout continues to work, only Alt Gr is gone. So far only loging out and
> in cures the problem.
>
> Anyone has a clue to what causes this?

Same problem here. It seems to be new, I'm on R14.0.2 (on Mint). I haven't observed this before.
I searched for a work around without necessity to log out (to many open windows to restall) and I 
found one. I opened the Keyboard Layout dialog and un-checked the Enable Keyboard Layouts" 
(switched it off" and voila, the Alt-Gr reapears again.

Now a solution but better than nothing.
Gerhard