Moving light lines on dark background

I have some problem with rather simple 2-D OpenGL scenes. There is some number of lines, for example, on a background (which filled with glClear). When I drag mouse, I “move” scene, recalculating translation and repainting. If background is bright (white, for ex.) and lines are dark (black, for ex.), all OK. On the contrary if lines are light and background is dark when I drag the scene lines becomes much darker, being almost invisible. When I stop dragging they recover immideately.
Does somebody knows what can it be?

Yeah, stop using a crappy LCD screen. Try any CRT instead !

Seriously, this ghosting effect is caused by the (slow) non linear response of liquid crystals. Recent screens sometimes have an “overdrive” system to force crystals to change state faster… but sometimes is it tuned too high, and you see reverse-ghosting when dark-grey moves aside light-grey for example.

Try to find an LCD screen with user-tunable overdrive !
For example you can read this for enlightenment :

Thanks much for an answer and explanation.