[ubuntu] Clicking on application launcher starts another window. What should I do?

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http://ubuntuforums.org – If I remember correctly, clicking on the application in launcher started the application if it was not already open and focused on the application if it was already open. I had to middle click to start another instance. But, recently, whenever I click in the launcher, a new application window is started, irrespective of whether one is already open or not. What should I do? A bug? Or a new feature? I am using 12.04 LTS and 12.10 in two machines. Both fully updated. Both are showing the same behaviour. (Hardware)