Taking the image posted earlier with obvious CA, I was able to remove most of the purple and magenta fringing by adjusting those colors' saturation to zero from 100 and their luminance to something below 100. I was able to mostly avoid artifacting here. I was, however, quite disappointed that Lightroom 3's Chromatic Aberration tool was outright useless- it had no affect whatsoever.
What you have here is an example of Longitudinal CA, sometimes abbreviated to LoCA, which is seen in lenses with residual spherical aberration. It is caused by different wavelengths of light rays focusing at different distances from the lens and shows up mainly when the lens is focused on close-up subjects. This is a lens issue; most fast lenses have some degree of LoCA. The way to get rid of it is to stop down the aperture to a smaller value, although some lenses (usually high end ones) are apochromatic (or near-apo) and can diminish or eliminate this artefact.
Unlike the more commonly known Lateral CA (LaCA), LoCA is a lot harder for image processing software to fix. Lightroom will remove LaCA without any problems, but LoCA is a tougher problem for it. Some newer Canon bodies are now able to remove LoCA in-body. If it really bugs you, there are 3 things you can do to fix it (in order of cost and hassle):
1. stop down when shooting close-up subjects (try f/4-f/16 range; any smaller and you'll run into diffraction on APS-C bodies - stopping down will also increase your DoF, which may be undesirable depending on composition)
2. manually edit it out in post
3. get a lens without (or with less) residual spherical abberations.
A quick way to test the susceptibility of a lens to LoCA is to focus on a close up subject (traditionally, a ruler with markings) and to stop down the lens. If the focus point shifts when stopped down, the lens has residual SA and will probably exhibit LoCA in the field. Since most people don't use their fast zooms for macro shots, and msot people don't shoot wide open for macro, LoCA is generally not a big issue for most users.
EDIT: Some lenses and lensmakers intentionally undercorrect spherical aberration to get smoother-looking bokeh, so like everything in photography, eliminating LoCA can be a tradeoff.
Wind, Sand and Stars.