I tried the uninstall driver technique without success. After the “Discover New Hardware” step it would just fail the same way.
I did just find a way that worked though. I re-installed the firmware. Not via the Sansa Updater. That program would just note that my Clip+ reported the most recent version, then give up.
Instead I manually re-installed the firmware using the process that Mac and Linux people have to use. detailed at
http://forums.sandisk.com/t5/Clip-Clip/Sansa-Clip-Firmware-Update-01-02-15/td-p/150227
Briefly, it is to download the zip frime at
http://mp3support.sandisk.com/firmware/clipplus/clipplus01.02.15.zip
Unizip it, and move the two files in the root of the Clip+ while it is mounted in MSC mode.
When unplugged it updates the firmware.
I don’t know if it was a necessary step or not, but I also reformated the Clip+ from its menu. In any event, it now mounts in MTP. mode.
