Just wanted to relay something about these two issues on a Sandisk Clip+.
Recently, my player would freeze about one quarter of the way through the progress bar when refreshing media but only when the mini-SD card was installed. Tried several known good cards and same issue. At the same time it failed the device driver in Windows unless I changed to MSC mode. You can change the USB mode under settings from the player’s menu. The player itself worked just fine without mini-SD card installed.
I tried all the advice here: http://kb.sandisk.com/app/answers/detail/a_id/42 but nothing worked. Then I tried something really simple. The USB mode by default is set to Auto Detect. When I chaged back from MSC mode, I chose MTP mode instead of Auto. Everything is back to normal. Windows detects the player, loads the driver and mounts device. The progress bar does not freeze anymore.
Hope this helps someone.