Downstream report: 

https://bugzilla.redhat.com/show_bug.cgi?id=707000

"there seems to be an issue with uninitialized memory which is detected by
MALLOC_PERTURB_:

$ env MALLOC_PERTURB_=23 xfce4-appearance-settings
(xfce4-appearance-settings:21153): Pango-WARNING **: Invalid UTF-8 string
passed to pango_layout_set_text()
...

and displayed content is broken. valgrind reports here


==20995== Invalid read of size 1
==20995==    at 0x4A06D82: strlen (mc_replace_strmem.c:282)
==20995==    by 0x3507A60251: g_strdup (in /lib64/libglib-2.0.so.0.2800.6)
==20995==    by 0x35086381CC: ??? (in /lib64/libgobject-2.0.so.0.2800.6)
==20995==    by 0x4FA6C4F: ??? (in /usr/lib64/libgtk-x11-2.0.so.0.2400.4)
==20995==    by 0x4FA7988: gtk_list_store_set_valist (in
/usr/lib64/libgtk-x11-2.0.so.0.2400.4)
==20995==    by 0x4FA7A86: gtk_list_store_set (in
/usr/lib64/libgtk-x11-2.0.so.0.2400.4)
==20995==    by 0x403876: ??? (in /usr/bin/xfce4-appearance-settings)
==20995==    by 0x402B4B: ??? (in /usr/bin/xfce4-appearance-settings)
==20995==    by 0x3504A2143C: (below main) (in /lib64/libc-2.13.90.so)
==20995==  Address 0xc97d873 is 67 bytes inside a block of size 4,096 free'd
==20995==    at 0x4A0556E: free (vg_replace_malloc.c:366)
==20995==    by 0x3507A49AC2: g_free (in /lib64/libglib-2.0.so.0.2800.6)
==20995==    by 0x3507A630F7: g_string_chunk_free (in
/lib64/libglib-2.0.so.0.2800.6)
==20995==    by 0x3508A07723: xfce_rc_close (in
/usr/lib64/libxfce4util.so.4.1.1)
==20995==    by 0x40382D: ??? (in /usr/bin/xfce4-appearance-settings)
==20995==    by 0x402B4B: ??? (in /usr/bin/xfce4-appearance-settings)
==20995==    by 0x3504A2143C: (below main) (in /lib64/libc-2.13.90.so)


Version-Release number of selected component (if applicable):

xfce4-settings-4.8.1-4.fc15.x86_64"