From the above link, I found this. I hope it helps..
Originally Posted by Shopaholic
I'm not a Mac user but I'm going to guess it's the same way as on PC. When the reader is attached to your computer click on the Sync button then uncheck the various things you have checked off. Make sure none are checked and that's it.
When you have anything checked off it will try to sync to that when the unit is connected. When nothing is checked off it's not going to try to sync. HTH
I just got a reader too and find that the sync is a bit wonky. Sony support said to turn off the auto-sync and that's how explained how to. He told me drag and drop was the best but I'm stubborn. Like the sync because then it would save my bookmarks back and forth. LOL