I tried both AVS Video Editor & AVS Video Converter to convert an avi-format file to a mp4-format file. In both cases, after the mp4 file was rendered, I used Windows Explorer to key-in descriptive text in its metadada. Within Windows Explorer, I did this by right-clicking on the mp4 file's icon, clicking on Properties, and then clicking the Details tab. Then, I proceeded to enter text in one of the Title, Subtitle, &/or Comments fields. Then I clicked OK and it took a while (several minutes) for it to make the change. Once the change was made, the file's picture icon was lost and the mp4 file became unplayable, giving a nondescriptive error message. Could it be that the AVS software is putting some crucial data in the mp4-file's area designed for the file's user to key-in file descriptions & file notes? I have included 2 screen captures of the mp4-file's metadata fields, that if filled-in, would corrupt the file and make it unplayable. I have entered data on these fields of other mp4 files before, and it did not corrupt the files. What could be the problem?