iTunes can change mp3 tags but mp3tag cannot

I am using v2.49 and I keep finding mp3 files that I cannot change the tags.
I know the files can be edited with iTunes.
It is not the software because v2.49 works correctly on other files.
No errors message, the software just chirps that the change is made but nothing is altered.
I cannot find anything marked read-only in the file or folders.
What should I be looking for that would cause this to not work?

John

Make sure your tag type has not got APE tags in them. And run with tag type ID3v.2.3.

Follow this post.

It should solve your problem. Do this before you try tagging your files. Let me know how you get on.

New information:

Nothing is wrong with the mp3 files I cannot edit on my laptop.
I must have a setting wrong/bad on mp3tag.

I cannot edit the mp3 files with mp3tag on my laptop.
But I can update the same files with mp3tag on another CPU.
And I can edit tags of the same files with iTunes, but yuck, who wants that?

On the laptop, I get the message that a tag is changed but nothing changes.
I must have a setting on my laptop that is different than my other CPU.

Help. I've even upgraded to 2.49b on my laptop yesterday but nothing changed.

And? Did you check, as Stevehero suggested, the settings in Tools>Options>Mpeg?
Are they the same on both PCs?
Anyway: you should set
read: APE, V1 and V2
write: V2 (and perhaps V1)
Delete: APE, V1