I am also severely affected by this bug in Natty and desperately looking at least for a workaround. Below there is a stack trace of my simple gtk-application crashing in pixman_image_composite32() - I'm not sure if that helps. I would really appreciate a fix of libpixman-1-0 for Natty. 

pixman_image_composite32                                    
      in /usr/lib/libpixman-1.so.0 at [0x7f57597aea60]
pixman_image_composite32                                    
      in /usr/lib/libpixman-1.so.0 at [0x7f57597aea60]
/usr/lib/libcairo.so.2(+0x3b98a)[0x7f5764a6898a]
/usr/lib/libcairo.so.2(+0x3cbc7)[0x7f5764a69bc7]
/usr/lib/libcairo.so.2(+0x6a83c)[0x7f5764a9783c]
/usr/lib/libcairo.so.2(+0x48b00)[0x7f5764a75b00]
/usr/lib/libcairo.so.2(+0x4c515)[0x7f5764a79515]
/usr/lib/libcairo.so.2(+0x4c866)[0x7f5764a79866]
/usr/lib/libcairo.so.2(+0x49181)[0x7f5764a76181]
/usr/lib/libcairo.so.2(+0x22ec0)[0x7f5764a4fec0]
cairo_fill_preserve                                         
      in /usr/lib/libcairo.so.2 at [0x7f5764a46c50]
cairo_fill                                                  
      in /usr/lib/libcairo.so.2 at [0x7f5764a46c69]
Oxygen::StyleHelper::verticalGradient(Oxygen::ColorUtils::Rgba const&, int)
      in /usr/lib/gtk-2.0/2.10.0/engines/liboxygen-gtk.so at [0x7f575382b733]
Oxygen::Style::renderWindowBackground(_cairo*, _GdkDrawable*, _GtkWidget*, _GdkRectangle*, int, int, int, int, Oxygen::StyleOptions const&, Oxygen::Flags<Oxygen::TileSet::Tile>)
      in /usr/lib/gtk-2.0/2.10.0/engines/liboxygen-gtk.so at [0x7f57538082ef]
/usr/lib/gtk-2.0/2.10.0/engines/liboxygen-gtk.so(+0xc1955)[0x7f5753842955]
/usr/lib/libgtk-x11-2.0.so.0(+0x263606)[0x7f5764f51606]
/usr/lib/libgtk-x11-2.0.so.0(+0x268e8c)[0x7f5764f56e8c]
Gtk::Widget_Class::realize_callback(_GtkWidget*)            
      in /usr/lib/libgtkmm-2.4.so.1 at [0x7f5763ddf76d]
g_closure_invoke                                            
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576581281c]
/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(+0x1f7e3)[0x7f57658237e3]
g_signal_emit_valist                                        
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576582d258]
g_signal_emit                                               
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576582d41f]
gtk_widget_realize                                          
      in /usr/lib/libgtk-x11-2.0.so.0 at [0x7f5764f4929e]
/usr/lib/libgtk-x11-2.0.so.0(+0x2658d8)[0x7f5764f538d8]
Gtk::Widget_Class::show_callback(_GtkWidget*)               
      in /usr/lib/libgtkmm-2.4.so.1 at [0x7f5763ddf9ed]
g_closure_invoke                                            
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576581281c]
/usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(+0x1f7e3)[0x7f57658237e3]
g_signal_emit_valist                                        
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576582d258]
g_signal_emit                                               
      in /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 at [0x7f576582d41f]
gtk_widget_show                                             
      in /usr/lib/libgtk-x11-2.0.so.0 at [0x7f5764f4a256]
PS_MainWindow_glade::PS_MainWindow_glade()                  
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f57681f52a0]
PS_MainWindow::PS_MainWindow(PS_Gui*)                       
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f57682156e0]
PS_Gui::createGtkContext(int, char**)                       
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f5767ec2fe6]
PS_Gui::PS_Gui(boost::weak_ptr<PS_Context const> const&, int, char**)
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f5767ec9006]
PS_Gui::create(boost::weak_ptr<PS_Context const> const&, int, char**)
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f5767ec9247]
PS_InitGuiProcessor::runProcessor(int, char**, void*)       
      in /home/flo/Projects/pasimodo/bin/../build/release/src/libpasimodo_gui.so at [0x7f5767ee3feb]
main                                                        
      in /home/flo/Projects/pasimodo/bin/../build/release/src/pasimodo at [0x40cf9d]
__libc_start_main                                           
      in /lib/x86_64-linux-gnu/libc.so.6 at [0x7f576e73aeff]
/home/flo/Projects/pasimodo/bin/../build/release/src/pasimodo[0x40c459]