After performing a system cleanup with the “janitor"and installing a theme manager “Art manager” the application simply disappear (the one with the minimise restore and maximise buttons).

The solution for it was installing/reinstalling some packages from synaptic :

• search using “Windows manager”

• select:

• metacity - A lightweight GTK2 based Window Manager

• libmetacity0 - library of lightweight GTK2 based Window Manager

• metacity-common - Shared files of lightweight GTK2 based Window Manager

• select “Mark for re-installation”