this is a sandisk issue!
I am having the same issue - my clip+ totally stopped working. Resetting has not worked, nor has leaving it plugged in to my computer for days. I have been trying to get in touch with Sansa to organise a return (I bought it in May) but have had no response - any ideas folks?
I love my clip+ but am disappointed at not being able to use it and am not getting any customer service...