Problem:
Performed sudo apt-get remove ubuntu-desktop and then installed xfce.
Now, I can't use tab-complete in any Terminal app in xfce when using VNC to access the box. It still works properly over SSH.
Solving:
# Open with a text editor ( vim, nano, gedit, etc ) the file
~/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-keyboard-shortcuts.xml
# Find the line
<property name=”<Super>Tab” type=”string” value=”switch_window_key”/>
# Replace it with
<property name=”<Super>Tab” type=”empty”/>
# Restart the X session
reference:
http://www.ubuntu.com/
http://www.xfce.org/