I just had that error yesterday. I finally got my 2 new 32 GB USB Devices before Christmas (Yeah :)
I just synced several playlists via the RB Sync Manager. Unfortunately, I forgot to rename the USB Sticks and did that after the playlists were synced.
So before renaming the USB Stick, my CDJ was able to read out the playlists and I was able to scroll through the lists as well, everything fine.
After renaming the USB devices in RB, my CDJ only got the Content just like you described as well.
Obviously, the CDJ was not able to read the data probably after the renaming process. Now I need to re sync both devices and rename before sync process. I addition to that, after sync of the device, it is not possible to unmount the device while RB is running, you need to close RB and than it is possible to unmount device on mac. Sucks ;)
But after that process, it finally works ;)