I'm using v.2.49
I've noticed for several versions now that when I retrieve data from freedb.org to tag the files mp3tag mishandles the DISCID field. (In the 'options' section I have 'Copy disc ID to DISCID field' enabled.)
What happens is, if the ID value starts with one or more zeros, mp3tag will move the zeros to the end of the ID, such that 020B1C11 (Abbey Road) will end up as 20B1C110.
This is not a serious bug by any means, but I thought I'd let you know about it.
Thanks for a terrific piece of software!