Question regarding cocos2d-X Screen

Hello,
We are facing a problem while using cocos2d-x 0.12.0 (2012-03-05) version.
The screen shot below indicates the problem we are currently having.
Our current program settings are,

CCDirector::sharedDirector()->setDepthTest(false);
CCDirector::sharedDirector()->setProjection(kCCDirectorProjection2D);

With this setting we do not have problem frequently but off and on.
The symptoms are, when the new layer or sprite appears, randomly we are faced with shadow zone on the screen.
The shadow zone does not last for a long time. And it goes away when the screen changes.
We need to know if there is a solution to fix this problem or a modification that we can apply to possible fix this.
We urgently ask for your reply because we really wish to eliminate this problem A.S.A.P
Thank you and we patiently wait for your kind reply


screen.png (45.7 KB)