I've got TWO N800 so far with similar power won't on problem.(The 1st one I got on Jan. 11 from an online store(NCIX), I sent it back, paid the shipping myself, got the 2nd one on Feb. 4).
I don't understand why so many ppl having the similar problem yet no one make the complain to nokia. And simply sent your old one back can NOT solve the problem. You might end up getting another defective device just like me. And nokia canada really sucks. They don't even admit this existing problem. see what they said:
"we are unable to duplicate the problems you are experiencing with
your Nokia N800 Internet Tablet. Nokia does not comment on forums and
third party web site comments." Totally bureaucratic craps, and they asked me to send it to nokia US for repair, but they won't even send it back to canada after the fix because all n800 sold in canada are US model. I can only ask my friend in US to get it for me........
And I've contacted the retailer, they can only refund me for the device but I'll have to pay the shipping myself! I was so frustrated and angry and ............
I just checked the vote, out of 132 ppl, 55 have the similar power on problem, which is over 40%, yet nokia dosen't admit it!
So only if you guys all send a complain to nokia, it will take us customers seriously and try to find a fix quickly! And by the way, be careful about putting the device into a fridge, it'll void the warranty (I was told by a customer representative).

Or should we all try to file a group complain together?

By the way, for those considering buying N800, I highly recommend NOT to buy it, at least for now, it seems the whole batch(after 2008) is not right.