It seems to be an issue with the startup of Xgl session.
Disabling Xgl autostart (create a file named ~/.config/xserver-xgl/disable) solves this issue.
The way xgl starts has changed recently. I'm trying to find out why it works just after boot time and not after the next logout/login.
If you want to help the script to investigate is /usr/share/xserver-xgl/Xgl-session. Seems to be a pb with acquiring a free display number.
By the way in my case disabling it enables NV-GLX extension instead of SGI-GLX.
It seems to be an issue with the startup of Xgl session.
Disabling Xgl autostart (create a file named ~/.config/ xserver- xgl/disable) solves this issue.
The way xgl starts has changed recently. I'm trying to find out why it works just after boot time and not after the next logout/login.
If you want to help the script to investigate is /usr/share/ xserver- xgl/Xgl- session. Seems to be a pb with acquiring a free display number.
By the way in my case disabling it enables NV-GLX extension instead of SGI-GLX.