Please can you give us more information about you Cybook?
Which update do you try to do?
How many stickers do you have in the back?
Do you remember the last version of the firmware you had on it ?
When you press the reset button behind, and then the power button, what's happen? Does it display the bootscreen? or better the second boot screen? (the mini cybook with three dots)
Without more informations it's difficult to answer you...
Did you try to charge it all night (when the red light is turn on) and try to boot it the next morning?