Problem: Sometimes screen flickering on Samsung Ativ Windows 8

Hi,
I developed a cocos game for Windows 8. On my Samsung laptop it works just great. However,when I testing it on my Windows 8 tablet (Samsung Ativ Pro) from time to time my screen is kind of flickering on some of the scenes (not on every scene). I tried to set DepthTest to false and projection to 2D - no success. Did anyone noticed something like this? I will appreciate any help, Thanks.

Update: it looks like the flicker is due to FPS drop. The screen is being cleared, but the new frame is not draw fast enough (so I see a background for very short time). Any idea how to fix this?