I'm having the same issue here.
Disabling apparmor profile (permanently) as described here
(http://ask.xmodulo.com/disable-particular-apparmor-profile-ubuntu.html)
helped.
On Tue, 5 Jun 2018 20:25:21 +0200 Carsten Schoenert
<c.schoen...@t-online.de> wrote:
> Hi,
>
> On Mon, Jun 04, 2018 at 10:41:04AM +0200, g.gragnani wrote:
> > f I launch thunderbird the whole xsession (XFCE) locks.
> > I'm only able to move the mouse arrow (without any effect)
> > and switching to a character console by using Cttrl-Alt-F1 etc.
> > Killing thhunderbird does not solve the problem.
> >
> > The same happens in an other machine, with a different set of installed
> > packages, different hardware and running LXDE.
>
> you have apparmor installed and it's likely it may causing issues.
> Can you check the behaviour with a deactivated AppArmor profile and also
> a removed AppAprmor package?
>
> > Versions of packages thunderbird suggests:
> > ii apparmor 2.12-4
>
> Other possible candidates are sometime the kernel. But without a small
> set of logs it's quite impossible to track down the root of the issue.
>
> Regards
> Carsten
>
>
