qt vc++ qwt but opengl is not working although configured with opengl option

Dear Friends

I have just built qt in vc++ and also qwt. All are built sucessfully and I am able to run the examples.
When I configured qt in vc++ i din't omit opengl, i.e -no-opengl i dint mention in the configure option so opengl must be enable in my case.
But I have created a QGLWidget and trying to draw a curve on it, but its flickering . pictures are not clear.
Any idea from anyone why is it happening.

Should opengl be able to be used . I ppreciate any suggestions.