remote screen (Ubuntu 12.04) doesn't update

[Gelonida N]

Hi,

I enabled remote desktop access on my Ubuntu 12.04 host.
(Somehow this was much more difficult to find than on10.04.
I have the impression that most common features are easier to find in 
12.04, bot slightly less common features can only be found with google 
:-( , but perhaps this is just me still not being used to all the UI 
changes)

When connecting with TightVNC  to my machine, I see the initial screen. 
 From then on mouse moves and clicks and key presses are sent correctly 
to the server however the screen doesn't update  anymore and stays frozen.

With some googling I found some information.
If I interpreted it correctly the problem is related to some compiz 
graphics settings (perhaps only specific to some graphics cards)

One of the suggested 'solutions' is to switch from Unity 3D to Unity 2D.

Being new to Ubuntu I have some difficulties finding how to perform this 
switch.

Could tell me how to do this?