Sansa e260 - display is blank

I have a Sansa e260 that I have not used for a year or more.  Today I plugged it into my PC & the thumbwheel lights up but nothing else, the screen remains completely black.  It has now charged for several hours, still nothing.  It was stored in a cotton carry case in my bedroom so no humidity or temperature problems.  It was working well the last time I used it.  Any ideas?

Try a reset? Press and hold the power button for 20-30 secs. Release, then press the power button again momentarily to start it up.