It was discovered that /etc/shells had the following entry:
added to the end of this file and this caused havoc to many programs since python's function: libuser.get_user_shells() in module: libuser does not check if each shell in this list exists or is functional and so causes certain programs such as GDM, setroubleshootd and sealert to fail or hang.
Removing the /SENDMAIL/ANY/SHELL item from /etc/shells will allow GDM, and other programs that uses that python function to work.
I suspect that either sendmail, postfix, or possibly ISPConfig has added that line item in /etc/shells after installation but I am not sure which one of these applications made this change.
Please disregard my previous comments in changing the /usr/share/gdm/default.conf GraphicalThemes default settings found there.