[ubuntu] Unity is very sluggish in Ubuntu 16.04

Hello all,

I have upgraded to Ubuntu 16.04 several weeks ago (I am upgrading since 14.10, no clean install) and Unity was working O.K. After some updates, that I don't remember now what were, Unity stopped working correctly. No Unity is very slow, practically unusable.
Here is a picture of the desktop after logging in.
I've installed Ciamon just to use my laptop and it's O.K. but I would like to use Unity.

Edit: resetting Unity doesn't work.