Dear Friend,
Yes, I was little impatient to get the solution, so sorry for that.
I will try to recompile my main VI and see the result. Infact I had deleted the control all togather and made a new one and tested that in my main VI (with the same hanging result) before asking the question. And also the corrupt VI does not seems to be the answer as when we copy paste control to new VI we get same result.
I do perform some settings on graph control (set no. of plots, set color, line type of plots, set scale for different plots etc.) before displaying the data but they have worked for a long time in previous versions of labviews.
Regards
S. Singh