Unable to see sketch lines.

exit sketch mode and again do edit sketch.u will be able to see the sketch properly

I've run into this a couple of times in assembly sketches. I take it as a cue that my video buffer's overrun and I need to reboot my machine.
nVidia Quadro FX 540

In 2007, I can't see the sketch lines I make in sketch mode. It appears after I finish making a line but not when I click and drag my cursor.

Is there a setting in the options to make it appear??