Comment 8 for bug 783155

Same problem here. Trying to run Skype and use the GTK+ engine for Qt. This is what I get, and a lot of GDK_IS_PIXBUF (pixbuf) failed on the terminal:
** (<unknown>:3718): WARNING **: Pixbuf theme: Cannot load pixmap file /usr/share/themes/Aqua-Joy/gtk-2.0/ProgressBar/trough-progressbar-horiz.png: Unable to load image-loading mod
ule: /usr/lib/gdk-pixbuf-2.0/2.10.0/loaders/libpixbufloader-png.so: /usr/lib/gdk-pixbuf-2.0/2.10.0/loaders/libpixbufloader-png.so: wrong ELF class: ELFCLASS64

Aqua-Joy is the GTK theme I'm using. The file that can't be loaded varies. I can change the GTK theme, but the same error will show. It doesn't prevent Skype from running, but most graphical features are missing, like radio buttons, hover actions and check boxes.
If I change the GTK engine in Skype itself, all is fine and the elements are visible. But tooltips are unreadable, the background color and font color are almost the same (yellow/white). The tooltip text color is probably still taken from the Qt theme, because it's a dark theme. In other Qt apps that do work properly (and in Skype when GTK+ is chosen), I clearly see that the font is white.
Now I can't see the option that's enabled and the tooltip help at the same time. It's one or the other.