> our automatic nightly yum update has loaded glibc 2.5-58.
 > Since this morning, some users on some machines sometimes (I can't say 
 > It more clear) have no gnome panel.
 > Some of them can start it with gnome-panel, some do not.
 > For me it seems like a memory fault, something like no free alloc or 
 > something. It never happend befor the glibc update.

Same here. We have SL 5.5. Not sure if it is a pattern,
but all machines I have seen having the problem are 32-bit,
the 64-bit ones seem Ok for now. I am including below the
contents of an .xsession-errors file.

Miguel A. Lerma

--
  Miguel A. Lerma
  Math Comp Sys Admin
  Department of Mathematics  <[log in to unmask]>
  Northwestern University    <http://www.math.northwestern.edu/~mlerma/>
  2033 Sheridan Road         847-491-8020 (w)
  Evanston, IL 60208-2730    847-491-8906 (f)

-----------------------------------------------------------

/etc/gdm/PreSession/Default: Registering your session with utmp
/etc/gdm/PreSession/Default: running: /usr/bin/sessreg -a -u /var/run/utmp -x "/var/gdm/:0.Xservers" -h "" -l ":0" "mlerma"
localuser:mlerma being added to access control list
No profile for user 'mlerma' found
Launching a SCIM daemon with Socket FrontEnd...
Loading simple Config module ...
Creating backend ...
SESSION_MANAGER=local/cantor.math.northwestern.edu:/tmp/.ICE-unix/2955
Reading pinyin phrase lib failed
*** glibc detected *** gnome-panel: free(): invalid next size (fast): 0x086c5a00 ***
======= Backtrace: =========
/lib/libc.so.6[0xb3b6c5]
/lib/libc.so.6(cfree+0x59)[0xb3bb09]
/lib/libglib-2.0.so.0(g_free+0x31)[0x2b5d481]
/usr/lib/libbonobo-2.so.0[0x5d66a6]
/lib/libgobject-2.0.so.0(g_object_unref+0x16e)[0x2bfa1ee]
/usr/lib/libbonobo-2.so.0(bonobo_object_unref+0x1e7)[0x5d0937]
/usr/lib/libbonobo-2.so.0[0x5d672f]
/usr/lib/libbonobo-2.so.0[0x5c87a9]
/usr/lib/libbonobo-activation.so.4(_ORBIT_skel_small_Bonobo_GenericFactory_createObject+0x21)[0x19f1d1]
/usr/lib/libORBit-2.so.0(ORBit_c_stub_invoke+0x120)[0x145820]
/usr/lib/libbonobo-activation.so.4(Bonobo_GenericFactory_createObject+0x73)[0x1a0d93]
/usr/lib/libbonobo-activation.so.4(bonobo_activation_activate_shlib_server+0x263)[0x1a2e53]
/usr/lib/libbonobo-activation.so.4[0x1a37ce]
/usr/lib/libbonobo-activation.so.4[0x1a38fa]
/usr/lib/libORBit-2.so.0[0x137791]
/usr/lib/libORBit-2.so.0(giop_invoke_async+0x98)[0x131538]
/usr/lib/libORBit-2.so.0(giop_connection_handle_input+0x3b6)[0x134ab6]
/usr/lib/libORBit-2.so.0[0x15254d]
/usr/lib/libORBit-2.so.0[0x15542e]
/lib/libglib-2.0.so.0(g_main_context_dispatch+0x182)[0x2b561a2]
/lib/libglib-2.0.so.0[0x2b59196]
/lib/libglib-2.0.so.0(g_main_loop_run+0x1b7)[0x2b59557]
/usr/lib/libgtk-x11-2.0.so.0(gtk_main+0xb4)[0x2f77c54]
gnome-panel(main+0x1ac)[0x805fb5c]
/lib/libc.so.6(__libc_start_main+0xdc)[0xae7e9c]
gnome-panel[0x805ef61]
[...]