I have found a solution to a most annoying yet undocumented problem when dealing with ProRes 422 or ProRes 422 HQ footage round-tripped from Final Cut Pro X to Davinci Resolve back to FCPX with the Neat Video Noise Reduction filter then applied. In short, the noise reduction filter would cause certain frames, up to hundreds of them in a 20 minute video, to look like this:
This issue was a pain to fix as you had to duplicate your video track and layer it on top of the corrupted frames one at a time. I figured out that even if your camera shoots in 4:2:2 color sampling, if you export unedited footage from your NLE in the ProRes 4444 codec, import into Resolve (I'm using version 9.1), apply your grades, and export as ProRes 4444, import resulting files back into Final Cut, and apply the Neat Video noise reduction filter, there aren't any corrupt frames.
From here you can export finished project as whatever you like, although I would suggest first converting back to 422 before compressing with h.264 as you will reduce filesize without reducing quality IF your camera uses 4:2:2 or lower color sampling ratio. I hope this helps and I'm using Final Cut Pro 10.0.7 on Mountain Lion 10.8.2. I hope this article helps people as I searched for it and could not find it, and after finding a solution wrote it myself!