Exception Error in my application.

Hi friends , I am working on a software for data acquisition system. I have almost completed the application . I need to retrive data from serial port save it to a db and plot Graphs with the values i have acquired. I have done all the things needed but now when i try to plot graph's i get a exception error after some time when Graphs have started plotting. I am not able to figure out what is wrong in my program , Cause i don't get any errors or warnings. I feel its a memory problem but i don't know how to solve it. Can any one kindly suggest what i have to do. I will post the code also if needed.

I bacially have a window with many qwtPlot widgets with 4 , 8 , or 10 qwtplot widgets. More the number of qwtplot widgets i select to plot the sooner i get the exception error. If i just plot one curve with one qwtplot widget i get the error after a long time.

I have attached the screen shot of the image.

Thank You