I have the same problem here. I've switched to kdm temporarily, I'm waiting for an update to gware gnome.
Code:
bash-3.1# ldd /usr/sbin/gdm-binary
linux-gate.so.1 => (0xffffe000)
libcrypt.so.1 => /lib/tls/libcrypt.so.1 (0xa7f68000)
libnsl.so.1 => /lib/tls/libnsl.so.1 (0xa7f52000)
libgtk-x11-2.0.so.0 => /usr/lib/libgtk-x11-2.0.so.0 (0xa7c60000)
libatk-1.0.so.0 => /usr/lib/libatk-1.0.so.0 (0xa7c46000)
libpopt.so.0 => /usr/lib/libpopt.so.0 (0xa7c3e000)
libXinerama.so.1 => /usr/X11R6/lib/libXinerama.so.1 (0xa7c3b000)
libgdk-x11-2.0.so.0 => /usr/lib/libgdk-x11-2.0.so.0 (0xa7bba000)
libgdk_pixbuf-2.0.so.0 => /usr/lib/libgdk_pixbuf-2.0.so.0 (0xa7ba4000)
libpangocairo-1.0.so.0 => /usr/lib/libpangocairo-1.0.so.0 (0xa7b9d000)
libpangoft2-1.0.so.0 => /usr/lib/libpangoft2-1.0.so.0 (0xa7b78000)
libpango-1.0.so.0 => /usr/lib/libpango-1.0.so.0 (0xa7b40000)
libcairo.so.2 => /usr/lib/libcairo.so.2 (0xa7af7000)
libXrender.so.1 => /usr/X11R6/lib/libXrender.so.1 (0xa7aed000)
libX11.so.6 => /usr/X11R6/lib/libX11.so.6 (0xa7a20000)
libXext.so.6 => /usr/X11R6/lib/libXext.so.6 (0xa7a12000)
libpng12.so.0 => /usr/lib/libpng12.so.0 (0xa79e1000)
libglitz.so.1 => /usr/lib/libglitz.so.1 (0xa79bb000)
libfontconfig.so.1 => /usr/X11R6/lib/libfontconfig.so.1 (0xa7995000)
libexpat.so.0 => /usr/lib/libexpat.so.0 (0xa7974000)
libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0xa790a000)
libz.so.1 => /usr/lib/libz.so.1 (0xa78f8000)
libm.so.6 => /lib/tls/libm.so.6 (0xa78d5000)
libgobject-2.0.so.0 => /usr/lib/libgobject-2.0.so.0 (0xa789c000)
libgmodule-2.0.so.0 => /usr/lib/libgmodule-2.0.so.0 (0xa7898000)
libdl.so.2 => /lib/tls/libdl.so.2 (0xa7893000)
libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0xa7810000)
libc.so.6 => /lib/tls/libc.so.6 (0xa76e1000)
libXrandr.so.2 => /usr/X11R6/lib/libXrandr.so.2 (0xa76dd000)
libXi.so.6 => /usr/X11R6/lib/libXi.so.6 (0xa76d5000)
libXcursor.so.1 => /usr/X11R6/lib/libXcursor.so.1 (0xa76cb000)
libXfixes.so.3 => /usr/X11R6/lib/libXfixes.so.3 (0xa76c6000)
/lib/ld-linux.so.2 (0xa7fbb000)
Gtk 2.8.16 was working fine, thus I'd expect the 2.8.17 update to cause no problems. libpng may be the cause however.
Edit: I just realized that libpng hasn't been updated. Then maybe it's libgtk. I'll try to find the 2.8.16 package and try.