OK, got it.  Pull off the four rubber dots and remove the hidden screws.  With the Chumby face down, slide your finger nails along the front and back to release the four latch/tabs (3" in from one side, 2.5" in from the other). Pull back side up 1/8" (as far as it goes), then gently pull out the side panels to free their tabs, then the back will slide all the way off.  The memory chip is then exposed, slide the metal piece, and the chip falls out.  That's as far as I needed to go.