SOPC VIP throughput problem

hello,

I'm setting up a SOPC system using the VIP IP modules and now I'm bumping into a problem.

The VIP system is mixing two streams into a single 800x600 stream which is clocked out with a 75Hz framerate to screen,

One stream is a 640x480 video input stream from camera:

cvi (640x480) -> framebuffer -> mixer (din_1)

while the other is :

framereader (800x600) -> mixer (din_0, background layer)

However, the output to screen is displaying a single color (this color seems to be dark green) with a black frame on the left side of the screen.

Now, if I change either the first or the second stream, replacing with a testpattern generator, I'm able to display the video output to screen, but when I mix the two original streams, there is something going wrong.

I tried increasing the pixel FIFO size of the clocked video output module to 5000 pixels, but this did not help.

Can anyone tell why this i s happening ?