Unity Dash is not clickable

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http://askubuntu.com – Version 12.04, NVidia GeForce 8600 GS with driver 304.43 I switch to Unity 2D because 3D was very slow (intensive hard disk activity, seems related to 3D) The problem now is that the Unity panel is not clickable, i mean when the dash is opened i can write text and display programs icons, but the cursor act as there is no panel. When i click a (i.e.) program icon, the panel disappear and the action is done for the object who was under the dash. (HowTos)