Why does my custom shortcut reappear unexpectedly?

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http://askubuntu.com – I created a custom shortcut Ctrl+Alt+T that calls x-terminal-emulator. For some reason, it does not work (nothing happens when hitting the mapping). When I remove the shortcut, the built-in Launch terminal shortcut (which is also set to the same mapping) opens the terminal window as expected. The problem is when I restart my session after deleting the shortcut, it is recreated in the custom shortcut window. Do you have any idea why this shortcut is always recreated automatically after restarting a session? Do you have any idea how to fix this? I can't find a configuration file in my home (HowTos)