cannot draw

while drawing it does not show what I am drawing till I push mouse button up. for example if I am putting line between two points I cannot see line till I release mouse button. I resinstall soft but it does not help

What graphics card are you using? Is it possible that your graphics card does not support OpenGL?

it were working, than some moment it stopped, so it could not be because card, somwthing wrong with soft

What is your hardware setup?