Gah I'm having problems with my two Readers too, now. I charged it fully on Wednesday, and haven't used it. I pick it up today (Saturday), and it's down to two bars. Never had this problem prior to the firmware update. Grr!
Resetting it the first time seemed to fix it, but I'll be blowed if I'm going to have to keep resetting it EVERY time I charge the thing.
Bah.