Glitch in materials?

I was playing around with animating materials…rgb ipos.
After animating a little sequence with particle hair changing colors, I tried to render it, but no matter what I do, the particles always stay the same color.
They change in the 3d window, though…
What do you think?
http://img379.imageshack.us/img379/5900/b3dcolorglitchmp3.jpg

reinitialize the preview renderer by closing it and re-open it.