It has been reported that the gnome-settings-daemon may crash on Red Hat 6. The problem has also been reported on Centos and Fedora.

If the output of the gnome-settings-daemon, executed in a terminal, is similar to the following:

/usr/libexec/gnome-settings-daemon

Gdk-ERROR **: The program 'gnome-settings-daemon' received an X Window System error.
This probably reflects a bug in the program.
The error was 'XI_BadClass (invalid Class parameter)'.

it is likely to be a known problem of libxklavier when the DevicePresence is
not supported (like in NX 3.4).

A workaround consists in disabling the keyboard plugin in gnome-settings-daemon. To do so:

• Run gconf-editor.
• Move to /apps/gnome_settings_daemon/plugins/keyboard
• And uncheck the "Active" box.

For more information you may refer to:
http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/4/html/Desktop_Deployment_Guide/s1-ddg-intro-gconf-default-mandatory.html

The long term solution consists in looking for a libxklavier version to fix this problem.