I hope that it is only iTunes that has problems and not you personally 
No, seriously: iTunes is VERY reluctant to update the database. So what you see after you have deleted (blanked) the field with MP3tag is the contents of the iTunes database.
You would have to update that database.
The easiest would be to delete the entry for the track in iTunes and then reread the folder where the track is.
A not as easy way would be to start a shell-script to update the database. Depending on the size of the database it takes a while.
For an example script, see here: Tagged everything but does not reflect in ITunes / else