Problems with firmware download and audiobooks

I just purchased this clip last week and am not very techinically oriented, hopefully someone can help. 
I bought it primarily to listen to audiobooks, which I can download from Netlibrary or Overdrive.  2 days ago, I downloaded an audiobook from netlibrary, acquired the license and transferred it to my clip.  (I also put some music files on it.) No problem with the sound quality, but had problems with the ff, got on this forum, found others with same problem. Followed instructions to update the firmware to 18. Now when I try to play the audiobook, it gives me this message: “Synchronize to continue music subscription” then it will either skip to play a song, or it will freeze up and I have to re-boot it.  I’ve tried deleting the audiobook and re-loading it, I’ve also tried deleting it, and downloading a new a/b and it still doesn’t work.  If it was a licensing problem, I would think I couldn’t play it on my pc/.  Any ideas?

Ok…you might have a bad license file on your device that it will keep popping up that message. … Best bet is format your device and reload everything…it should work now.

No, that didn’t work, anything else?

Are you in MTP or MSC mode?..for all DRM related contents, you should always have it in MTP mode or else it doesn’t work

That worked.  So what I figured I need to do is this.  I have to have it set to msc to transfer the audiobooks onto the clip, then change it to mtp to play the files.  Thanks!

Actually…you can transfer the audiobooks and anything else just in MTP mode alone…you don’t have to switch between MTP and MSC

Note:  MTP and MSC don’t talk to each other meaning that whatever you transfer in MTP mode…you will not see it in MSC mode and vice versa so my advice is, if MTP is working fine for you…keep it in MTP unless otherwise.

I have also a problem with audiobooks after firmwareupdate. The Sansa clip say that he “activate device with audible player this file” then the clip do nothing.

PS: Sorry my english is not my motherlanguage