The error persists even though the file has all the security properties to allow "Full control" for every user. And the file can be renamed in its folder, and MP3 has the same problem with the newly named file. The other 10 files in the folder all have tags. Select one, Ctrl-C and the select file #5 and Paste brings up the error.
Then it could be that this file has been corrupted.
So if you have the chance to rebuild it, that would be worth a try.
If the file is open elsewhere you will see this error as well. Like if a player has it selected, even if it is not playing.
The file is a FLAC music file. How do I "rebuild it?"
The file, the whole album, is open only in mp3tag. All the other files have tags and I tried to copy another file and past those tags into the one file. I don't think the single file could be open anywhere else.
Yes, I saw that. If it had been an MP3 I would have suggested to use one of the mp3 tools.
Now, I would assume that you have to look for an audio editor to load the file and save it again.
You can also first verify integrity with foobar2000: How to check files for errors?
Yet another way to check a lossless flac file for errors is to convert it to wav and then back to flac.
I am just curious: How does a conversion let you know if a FLAC file has errors?