It turns out that pressing the Esc key on which any window: terminal, the game (the window with the game, which the ESC responds with output such as a menu or a dialog with options), file manager - popup menu appears.

It is very annoying example of games that this function of Uni software locks out other games, and also to other programs in the popup menu Esc instead of withdrawing from the use of some options - means that you can not use xfce currently no programming, creating film or processing and photo editing, etc. because the menu on the Esc button causes the desktop becomes somewhat useless.