J'ai réussi à trouver ça dans le syslog de la machine hote
Oct 4 15:55:55 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Received a NET_CURRENT_DESKTOP message from a broken (outdated) client who sent a 0 timestamp
Oct 4 15:55:57 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x2e00017 (VM Dev)
Oct 4 15:55:57 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Received a NET_CURRENT_DESKTOP message from a broken (outdated) client who sent a 0 timestamp
Oct 4 15:55:57 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x2e00017 (VM Dev)
Oct 4 15:56:30 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Received a NET_CURRENT_DESKTOP message from a broken (outdated) client who sent a 0 timestamp
Oct 4 15:56:30 ange7 org.gnome.Shell.desktop[2294]: Window manager warning: Buggy client sent a _NET_ACTIVE_WINDOW message with a timestamp of 0 for 0x2e00017 (VM Dev)
Oct 4 15:57:25 ange7 kernel: [17189.498407] vboxnetflt: 0 out of 3658 packets were not sent (directed to host)