Same happens to me. I just emailed Nokia about it.

I also posted here (when I thought I knew how to get it back on):
http://www.internettablettalk.com/fo...ad.php?t=12731

This is what I wrote to Nokia:

My N810 does not power on anymore.

When I first got it out of the box, it only turned on after I left it on the charger for a while. I thought that would be normal, since I expected the battery to be empty.

Later I tuned the device off, while I was sure that the battery indicator indicated 3 hours left. I could not turn it back on. Pressing the button for 3 seconds had no result (led also stayed dark). I connected to the charger for a few minutes and then the charging icon appeared. With the charger still connected I could turn it on.

To test more, I turned it off, charged it overnight (in the off state) until the display showed the charging icon and the message to disconnect the charger to save energy. I disconnected the charger and tried to switch it on... nothing. I reconnected the charger: nothing happens, not even the charging icon in the middel of the screen appeared. The device just seems completely dead. I tried replacing the battery, removing the memory card. Nothing.

I measured the voltae of the battery, which was 4.06V (between pins + and -) which seems okay.

I remember havin a similar problem with my N800 in the beginning, but that was solved somehow (maybe new softare fixed it). The N800 even flashes the led as soon as you press the power button, even when the battery is completely empty. I would expect similar behavour on the N810. Also I would expect the N810 to show the Nokia logo as soon as you connect the charger.

I hope this is a known problem and that you have a solution.
BTW: I upgraded to the latest 2008 software as soon as I got the device.
(RX-44_2008SE_1.2007.42-19_PR_COMBINED_MR0_ARM.bin)