gdm login cannot display

Hi ,

Can anyone help, i have a z820 workstation install with redhat linux ws 6.7 . Someone install some apps on it and now after reboot a graphics screen show with mouse cursor but gdm login screen not showing . So i bypass it by using key ctrl alt f2 and I can login from prompt in text mode. There , I try to run startx which the gui started and I can see the desktop icon only inside the gnome-panel is not visible. Can someone advice??

Attach is the screen shot

Regards
Vincent