Ankit,
OK, thanks. Please, when you reply to emails, ensure that the "discuss-gnuradio" email address is included so the discussion can be seen on the mailing so it will help others.
So I would recommend adding some WX GUI components to your audio tone signal flow graph, and see if they work correctly (Like a WX FFT Sink). It looks like a problem with WX. If it does work, continue adding components to the simple flow graph to make it more like your larger one, until you can see which one fails.
If WX fails right away, take it off, switch the top_block to QT GUI mode, then add a Qt GUI component instead, and see if that works. If QT is working, then perhaps you can replicate the block from the tutorial with QT components. Most of the basic components come in either QT or WX flavors.
If you post the ".grc" file I will run it on my Windows install and see how it works.
Geof