MSP mode under Linux

For now I have my Clip+ set to work in MSP mode.  I can see its Internal Memory folder under Windows, and that folder contains Music, Playlists, etc.  I also was able to create a playlist there (using Winamp). However, under Disk Management it does not show up as a drive.

In Linux I see 4 folders for it:

    Canon PowerShot A1100

     MTP Device

     Sansa Clip+

     USB PTP Class Camera

For MTP Device and Sansa Clip+, if I try to open the folder I get a message “Could not read folder.  Could not lock the device”.

At one point I actually saw a subfolder under MTP Device which had Music, Playlists, etc.  But I had to reformat the device and that folder has not come back.

I’m able to use the device in MSC mode under LInux, but that has disadvantages compared with MTP mode.  So I’d like to understand what is going on here and if there’s some way to access either the Clip+ folder or MTP device, with the aim of accessing the underlying data.  

Can anyone tell me what is going on?