I think this problem is related to WMP 11b2 which somehow locks the tags from editing. To be specific, I opened a tag in MP3Tag, and tried to change the artist name in the right panel. After I typed the new name, I hit enter, and the old name reappeared. I then opened the same file in WMP, and used the "Advanced Tag Editor" and changed the tag. Have you or others heard anything about this kind of behaviour of tags in WMP?
I cant offer much as I only began using the program yesterday, but I am also using WMP11.
I entered my tags and included an image and it all worked fine.
The WMP version is 11.0.5838.4827