1) ctrl+alt+backspace注销切换到登录界面
2)左下角option里选择change section, 选择failsafe terminal
3)输入帐号密码进入后，在命令行输入gconf-editor
4)依次选择Desktop->Gnome->Applications->window_manager , 把两处/usr/bin/compiz改成/usr/bin/metacity
5)ctrl+alt+backspace注销切换到登录界面，change section 选择gnome
Good luck!