It appears that .ced files are saved on SD card in JVC digital cameras in cases when the card itself is formatted with unsupported or wrong file system. In any case, a .ced file seems to be just few kilobytes in size and is likely index or contains just some metadata so there is really no way how to convert it, or recover it to a video file (for example as the original MTS file).
Some users had some success with importing .ced file in iMovie for Mac. However, this may be due the fact that actual video track (.mts, .mod) was also recorded along the .ced files. This means that iMovie just used the .ced file as a link to the actual video recording and could import it. But in majority of cases, only .ced file is present and no video track so no import or conversion is possible.
This conversion entry was verified by us and conversion was flagged as wrong or not possible.
Usually this happens when the conversion would try to convert different types of data between each other, such as audio to image, or it is not possible because incompatibility between programs, caused by closed file formats, very limited support etc.
If you find entry that you feel is flagged as bad wrongly, please tell us in the discussion below with as much as information as possible so we can fix it.