Together with your other post
/t/14440/1
you seem to be having one heck of a weird setup. How is anybody to tell from the distance what seems to be the problem up your end.
Just a reminder: MP3tag is a Windows program. It runs properly on most Windows OS setups. What you have to do on a Mac ... I will not start a discussion on the preferences of systems but seems to be that in this application scenario the Mac environment does not seems to be the optimum choice.