This has nothing to do with DOpus nor 3.9. The CDDA icon is not a disk icon but an AppIcon maintained by CacheCDFS itself. IIRC the icon is stored in env:CDDA.info or env:def_CDDA.info. Read the CacheCDFS docs for more info (docs are contained in the IDEfix97 archive on Aminet).
Bye,
Thomas