Hi, I think I got a bug - whenever I add album art into some FLAC files, I got a file access error, and the file corrupts (cannot be played in VLC). I can't delete the corrupted file as well, since I got a Permissions error. I can reproduce this issue.
Take care that the user with which you edit the files has sufficient access rights.
It is not enough to be Administrator, you actually either have to modify the ownership or grant access for everybody.
Also, Mp3tag should be installed by the same user id that is supposed to use MP3tag in the end. Like that you avoid access permissions problems.
And: do not let at the same time other programs like WMP access the files that you want to edit. This may lead to lock errors. This behaviour applies especially to large FLAC files.
Interestingly enough, turning off the Windows Search service seems to have fixed the issue.