Why won't my Memo Pad 7 reboot after firmware update

This is the SECOND Asus 7 in a row that this has happened to me with. Both were manufacturer re-furb from a reputable online vendor.

Charged the battery -> 100%. Turn on and follow the initialization procedure (WiFi, locale etc etc)

Update everything in Play store - don't really have a choice about this one!

Finally go to settings, about, firmware upgrade. Download the update, get the little android update man and finally the device reboots. Partly.

All I get is te backlight (faintly) on a blank screen. I can turn the device off by holding the power button for the 8 seconds, but any reboot after that (normal or volume + power) gives only the same blank screen with a very faint backlight.

Any help greatly appreciated