Mouse volume control issue !

Hi ,
Since this morning I can’t control the faders with a mouse clic :
Usually to set up the fader to 0db I hit alt+clic on the fader but since this morning every time I hit clic on the fader (without the alt key) it goes straight to 0dB and the channel has a red rectangle around it ! I can’t reverse the behaviour !!! I’ve been searching the net and the manual … can’t find the process to reverse it !!! I’m going crazy !!! Thank you guys !!!

I have a video of the behaviour … if some one can help me … million thx …