Why does F10 in gnome-terminal open the right-click menu?

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http://unix.stackexchange.com – I am running Fedora 17 gnome (shell) 3 and gnome terminal I am a user of both gnome-terminal and midnight commander. As default gnome-terminal has always used F10 (which I need while using mc), to opening the top menu. So was this time. I was able to disable that behaviour in the settings, as always. Which is new to me, is that after I disabled the setting, it started opening the "right-click menu" at the mouse cursor when I press F10. The key goes to mc too, but it is annoying to have to always close the menu. I assume it is caused by gnome terminal, as it does not happen in other (HowTos)