Ubuntu 16.04 gdk-pixbuf issue "Unrecognized image file format"

[bla-]

Hello everyone,
I'm struggling with a gdk-pixbuf issue. Unity will segfault on start, I can manually start xfwm4. But GTK applications either crash or start without icons and many error messages such as "Gtk-WARNING **: Error loading theme icon 'gtk-convert' for stock: Unrecognized image file format". Looking at the syslog reveal error messages such as "Oct 25 10:14:23 xxxxx gnome-session[29961]: (nm-applet:30339): Gtk-WARNING **: Error loading image 'file:///usr/share/themes/Ambiance/gtk-3.0/assets/entry.png': Unrecognized image file format
Oct 25 10:14:23 xxxxx gnome-session[29961]: (nm-applet:30339): Gtk-WARNING **: Error loading image 'file:///usr/share/themes/Ambiance/gtk-3.0/assets/entry-disabled.png': Unrecognized image file format"

The files are there and valid pngs. SVGs also do not work. I tried to reinstall gdk-pixbuf,libpng* but it didn't help. I also tried to update the mime database and regenerate gdk-pixbuffer loaders.cache.
Any hint what might be wrong or how to debug this?
Thanks!
Jan

[mc4man]

No real clue but if you're mixing DE's then generally a poor idea. Just to see what's this report?

dpkg -l | grep libglib

[bla-]

I'm not mixing desktop enviroments, I normally run regular unity. Running xfwm4 was just a quick test to check if x is completely broken or if it is just unity.

Here is the output from dpkg:

ii libglib2.0-0:amd64 2.48.1-1~ubuntu16.04.1 amd64 GLib library of C routines
ii libglib2.0-0:i386 2.48.1-1~ubuntu16.04.1 i386 GLib library of C routines
ii libglib2.0-bin 2.48.1-1~ubuntu16.04.1 amd64 Programs for the GLib library
ii libglib2.0-data 2.48.1-1~ubuntu16.04.1 all Common files for GLib library
ii libglib2.0-dev 2.48.1-1~ubuntu16.04.1 amd64 Development files for the GLib library
ii libglib2.0-doc 2.48.1-1~ubuntu16.04.1 all Documentation files for the GLib library
rc libglibmm-2.4-1c2a:amd64 2.39.93-0ubuntu1 amd64 C++ wrapper for the GLib toolkit (shared libraries)
ii libglibmm-2.4-1v5:amd64 2.46.3-1 amd64 C++ wrapper for the GLib toolkit (shared libraries)

[bla-]

Issue solved. Missing read permissions in /usr/share/mime. Was likely caused by a buggy closed source installer