I had some discussions with the programmer of Tag&Rename a few years ago (sadly, he seems to have vanished and the program appears to be abandonware...). Anyway, he explained that to accommodate all of the different ways that people liked to use the Disc No. field, he treats it as a text field rather than a numeric field. So 5/9 is actually text "5/9" in T&R while most applications view that field as number, so the field in programs like DO is just 5.
Thanks for that. I could probably cope with that by changing the code in my macro, but the solution seems even simpler. Save the IDv32 tags in ASCII instead of Unicode.
All seems fine now. Sorry to hear that Tag n Rename may be abandonware, it's a neat little program. I did get an upgrade not that long ago and Softpointer are still selling it - even indicating that version 4 may be on the way.