Thx 4 your answer DGillespie.

The problem started when I installed the demo a few days ago. It sounded to me like some nasty limitation. So I bought the plug.

It did some new tests today, il happens also whith EQuivocate. It is strange , the audio goes on , the mouse still moves but all windows are frozen during 10 sec ( even non audio apps open in background like firefox… ) then every thing come back to normal. Never had a problem like that with my setup.

I will do some more tests tonight with Presonus studio one. I was wondering also about my old OSX 10.9.5.

Thanx for your help.