File 'cannot be opened for writing'

When I try to change the tag on a file, I get error message that the file 'cannot be opened for writing'

Help please !

What kind of file is it?
Or perhaps have a look at this thread: /t/12416/1
or this one: [X] .wav cannot be opened for writing replicable bug

I seem to have solved - need to remove existing tags first.

Thanks for answer.