"MTP DB Mismatch Format?"
I had the same problem In My Sandisk Sansa, and the way I fixed it is the following:
Plug your player in your computer in MSC mode (On your player, go to settings, then USB and choose MSC)
Then in "my computer", right-click on the player icon and go to "properties".
In "properties" go to "tools" and in the first option, which is "error checking", click on "check now".
In check disk options, check both "automatically fix file system errors" and "Scan for and attempt recorevy of ba sectors".
It's going to take a few minutes (phase 1 and phase 2 will be displayed). Wait until it is complete.
When it is done, close the "properties" window and right-click on the icon of the player and click on "format"!
It should say format complete and the player should be then be ready to synchronize files again!
Now Enjoy That