With some more research this AM: SOLVED! The extension "CDSD..." is installed as part of Roxio's CD Spin Doctor application (which is a "bonus" program included as part of Roxio's Toast application package) and is unrelated to the FTIUSB driver or to the Arduino software.
There is more info at http://discussions.apple.com/thread.jspa?threadID=2158125&tstart=60
, but the bottom line is that we can ignore this error msg as far as Arduino is concerned; it can also be ignored as far as Toast itself is concerned: only the CD Spin Doctor application is affected. And if you use CDSD there is now (as of just last month) an update available online from Roxio. (You have to DL the entire Toast update, to v. 10.0.6a.)