I have noticed that if I opt to write the compilation MP3 tag, CATraxx will set it always to true regardless if the compilation checkbox is selected in an album (unless the program I use to manage the tags outside CATraxx, Tagscanner, is wrong).

For the time being I have had to disable the writing of such tag.

Maybe it's the Tagscanner.

It does work here.

I am afraid you are right, and I was fooled by TagScanner. By checking with the Windows 7 Explorer details tab effectively it seems that TagScanner is not dealing properly with this bit of information. The behaviour I've noticed is not consistent, however, some data I've tagged from CATRaxx was shown effectively as part of compilation (and it shouldn't do it) from TagScanner, but once I cleared up the flag from within TagScanner the flag remained off.

Nevertheless, I apologize for the involountary confusion.