Thankyou Sir for your response. Sorry for replying late Sir. I didnot receive your mail so i had to go to the website and check it.
I tried to add the WX GUI FFT Sink to my audio tone signal flow graph.But after the execution the same error persists.
Then I changed the WX GUI Sink to QT GUI Sink, it was working well and the graph can also be seen.
So as you have mentioned, it is a problem with the WX components.
Below attached is the .grc file for my project.
Another doubt Sir is that,are all the WX components replacable by the QT components.
Thankyou