In Final Cut Pro, using the Color Corrector filter over the Cross Dissolve transition when applied to Freeze Frames sometimes causes a color inversion and posterization effect.

I've found two ways around this:
1. Use the 3-way color corrector instead, or any of the other color adjustment filters.
2. Apply the Color Corrector filter to the Freeze Frame in a new sequence. Then use that as a nested clip in the main sequence, and apply the Cross Dissolve to that nested clip.

Thanks much to "Sureal" for the second solution!