Ok, the issue comes from one of my monitor connected through a Displayport->HDMI passive adaptator.
If I unplug this monitor, I boot properly.
I tried plugin the monitor once on gnome desktop but all my screens turn black.
Again, my 3 monitors work fine in the live iso session.
Should I install arandr in the live iso, get the xrandr command line and run it once booted on my hard drive ?
I think the subject says it all.
1 out of my 3 monitors lights up in a very (very !) low resolution, blinking and displays only upper left part of desktop. I guess the driver crash for my graphic card.
I had to install XFCE and select autologin so I can do something :
Now, I can barely type command in a terminal (butI could write a shell script through live session which is working perfect)
But I cannot use add/remove program or anything else because of the low resolution.
Thanks for your help in sorting this out.
I guess it is a driver related issue.
How can I download and install a new one ?