using itunes to record minidiscs

I could be wrong, but I don't think that the Mac filesystem will recognise the MiniDisc and vice versa. MindDisc use the ATARC compression and won't play mp3's. You would need to do this the same as connecting, say, a cassette recorder. Out through the headphone socket on the Mac, in through the input on the MD, and record. You can't simply drag files across.

hth

Does the recorder appear in Finder as a Disk? If so, select the songs you want in iTunes and drag them to the Recorder's icon. Let us know what happens.