I use Xubuntu 14.04.1 on my PC. I don't know why but sometimes I turn on PC and see all menus and settings have returned to default settings, for example, wallpaper, language settings or taskbar menu. If I used Windows, I could say it may be a virus, but here I have no idea.
By the way, I have installed this distribution of Linux on another PC which has exactly the same configuration and it has no problem.
How can I fix this?