Did you noticed that in Lightroom 2 and 3, the tool "detail->Defringe->All edges" helps to reduce color noise especially at high ISO ?!
I have a lot of photos that seems to have no chromatic aberrations, but some color noise, and discover recently that in some case, the color noise reduction tool is not enough.
But "Defringe->All edges" helps me to almost completely remove that color noise.
Have a Nice Day.
Thierry