I don't use a MAC and have the same problem with duplicate songs.
I tried to erase the duplicates but like cfm56d7b, I found that I don't have duplicates! So, I thought I be smart and format the memory stick, reload the songs and solve the problem...well, now my car wont read the memory stick. It's like it's not even plugged in. WTF??? I'm going to try a different memory stick to see what happens but I haven't yet.
