if you have a problem where the computer fails to load the GUI (Graphical User Interface), meaning that if you dont see the taskbar, cannot click on icons, cannot close applicaions, etc, You have to restart your device (device that runs ubuntu such as Desktop and Laptops, Obviously.), or your "Power Off" or your GUI or UI doesn't work, etc, this will be a good solution for you.
I had this instance many times. Linux only loaded in the background and that's it. only the shortcuts worked.