Unity Launcher disappeared

[Bocheng Yang]

Hello,all
My menu bar and Unity launcher have disappeared in Ubuntu 14.04. Also
cannot access the terminal via ctrl + alt + t

I have tried many methods,but not OK.
Like:
*Removing some compiz files:*

> rm -r ~/.cache/compizconfig-1
> rm -r ~/.compiz


*Unity reset:*

> unity-reset


reinstall ubuntu-desktop

*dconf reset:（this did work before，but now I meet a error:Cannot autolaunch
D-Bus without X11 $DISPLAY)*

> dconf reset -f /org/compiz/
> unity --reset-icons &disown


Help get back unity launcher.(or switch another GNOME?)
Thanks~

PS:
I find if I use 'sudo apt-get dist-upgrade'  this command
I may meet this problems.(I have meet three or four times)
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