Rendering Problem Time Stretch

I have a face that has some radial fastblur. The color on the face is adjusted with curves. I have used time stretch to elongate the clip. I can watch the clip with quarter resolution, very nice, but I can not view it in full resolution, its not lagging but the red color starts to flicker. The same problem when I try to export, even at low resolution, both with full and quarter resolution. Whats wrong? I suspect the time stretch+curves. Here is a screendump: