Terminal stops working after closing a program windows started from the Terminal

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http://askubuntu.com – System: I have XUbuntu 12.04 64bit and run Terminal 0.4.8 (Xfce Terminal Emulator). Problem: My Terminal always stops to accept any input after I close a program window started from the Terminal. Details: For example, I start leafpad, (or geany, tkdiff etc) from the terminal. I close the window after finishing my job by either clicking on the close button or using ctrl-w. Then when I go back to the terminal, it does not accept any input any more. Workaround: When this happens, I have to click on any other window (giving it the focus) and go back to Terminal again. Usually this causes the (HowTos)