QuartusII sp2 web edition error using TPG

Yesterday I've set a simple video system:

test pattern generator (yCbCr 4:2:2 parallel 8bit per color plane)

chroma resampler 4:2:2 ->4:4:4

color space converter

Clocked video output

I don't know why, but sometimes compiling the project ad running it, I get only an half wihite and half magenta screen.

canceling chroma resampler and color space converter, getting a system

test pattern generator (RGB parallel 8bit per color plane)

Clocked video output

it REMAINS the same.

It seems to happen sometimes, even if I start a new project.

I don't know what should be the problem.

Any one colud help me?

best regards

Phate.