Found a fix but not the solution !
After searching this Pause problem , I find this post :
forum.xbmc.org/showthread.php?t=77937
The fix ( modify Pause to Play in the remote.xml) was the solution , now pausing a media no more making me loosing signal when I stop or at the end of it.
But it's a fix because , if a start playing music , stay in the menu , focus on a media file , if I push the Pause button , It don't stop the current playing file as expect but immediatly start playing the focus one.
Well It's a xbmc bug , see here
trac.xbmc.org/ticket/7338 , a patch exist here
trac.xbmc.org/attachment/ticket/7338/xbm...0110406-156f721.diff
I don't now if you could add it to the next openelec official build , but I hope this post could help other people. It fix my loose signal , but it also globally fix ( not resolve ) the no more menu sound.
I think the same patch ( but for Eden line number) than the stable realease one needs to be applied in actual Eden build because xbmc team has not correct it