valgrind invalid read

==22535== Invalid read of size 4
==22535== at 0x9E984AA: gnome_cups_request_execute_async_internal (gnome-cups-request.c:671)
==22535== by 0x9E98099: gnome_cups_request_execute_sync_internal (gnome-cups-request.c:544)
==22535== by 0x9E97FDD: gnome_cups_request_execute (gnome-cups-request.c:508)
==22535== by 0x9E91BED: get_printer_names (gnome-cups-printer.c:680)
==22535== by 0x9E91CCB: update_printers (gnome-cups-printer.c:720)
==22535== by 0x9E91DD2: update_printers_timeout (gnome-cups-printer.c:757)
==22535== by 0xB2B6F1A: (within /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0xB2B6A13: g_main_context_dispatch (in /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0xB2B985C: (within /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0xB2B9B69: g_main_loop_run (in /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0x67D3022: gtk_main (in /usr/lib/libgtk-x11-2.0.so.0.1000.11)
==22535== by 0x40DFC6: main (in /usr/bin/gnome-cups-manager)
==22535== Address 0x12ED05B8 is 8 bytes inside a block of size 88 free'd
==22535== at 0x4C2067E: free (vg_replace_malloc.c:233)
==22535== by 0x9E973F0: gnome_cups_request_struct_free (gnome-cups-request.c:220)
==22535== by 0x9E97665: idle_signal_request_complete (gnome-cups-request.c:259)
==22535== by 0x9E9768C: do_signal_complete (gnome-cups-request.c:268)
==22535== by 0x9E97B7D: request_thread_main (gnome-cups-request.c:381)
==22535== by 0xB2D4518: (within /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0xB2D2B73: (within /usr/lib/libglib-2.0.so.0.1200.11)
==22535== by 0xA76C2A4: start_thread (in /lib/libpthread-2.5.so)
==22535== by 0xB82A5EC: clone (in /lib/libc-2.5.so)