Modifying the RMD file by tweaking look settings in the REDCINE-X Pro caused After Effects to be unable to use media.
Version 30.33198 fixes RMD issue.
so what's the solution?
This was a while ago, but I think I went into REDCINE-X Pro at the time and clicked all the "D" buttons to set the metadata back to it's defaults. If that doesn't work, maybe try deleting the RMD file which contains metadata modifications. Also, notice that at the bottom of my post I indicated that the newer version of the software made resolved that problem, so try using newer software to open the media file which, I think, updates the RMD file and allows AE to use the R3D file.