New N800, came with OS2008 from factory. Normally, I turn on power by holding down the recessed power button until the blue light comes on for a few seconds, then the screen comes alive.

But sometimes.... it won't turn on, unless I add AC power.

Initially, I figured the battery was dead, but this often happens after charging overnight. When I put the AC charger back on, it starts immediately, so its not a bad switch. If I then remove the charger, the battery meter reports "10 days on standby", and a very long time in use. I don't think the battery is bad, it lasts for several days of occasional use.

I'm guessing there is a software problem, which is not seeing sufficient voltage to permit a startup. So far, I'm always able to start it immediately with AC power. Once started, it runs for days on battery.

Is this a known issue?

I have had that situation happen a couple of times. I tried a couple of things:

Change power outlets. I know it sounds trivial but it worked for me

OR

Make sure the power connector is completely seated in the receptacle. I have noticed that if it is not, it will not charge effectively and may do the exact opposite...DRAIN THE BATTERY.

I have this problem too - usually immediately after connecting or removing the power cable while the device is off. It won't turn on for a good 10-15minutes or so after that.

Annoying but no idea why. Tried removing the battery, pressing keys all sorts of things in the meanwhile, but makes no difference.

Yes, I've also tried removing the battery for a while. Makes no difference.

The first time I thought it might be that the charger wasn't inserted all the way, but its happened enough times now that I know that's not the problem. Also note that when I do jump-start it with AC power, then remove AC power, the battery monitor shows fully charged.

I believe this is a firmware issue, where the system won't allow itself to boot if below a certain voltage. Unfortunately, don't know how to fix it.

Yes, this look like some SW/HW problem in bootloader. This happens with some 770s too. What helps (at least with one 770 I have seen) is enabling R&D mode via linux USB flasher. When device is in R&D mode there are some shortcuts in poweron logic and whatever normally decides to disable poweron is skipped. This may be pure SW bug but may be also some sign of somewhat flaky hardware (i.e. some hardware selftest fails when power button is pressed).

With 770 some people believe this is early sign of WSOD but there is not enough information to confirm/deny it.

Best is probably to never turn device off. Luckily this is how the device is designed to be used.

But beware that with some (or maybe even all?) firmwares R&D mode may cause faster battery drain since it may enable some additional debugging stuff or prevent device from deep sleep or something. Again there is not enough information but sometimes someone from @nokia.com vaguely suggests that enabling R&D mode may have some unwanted side effects.

having said that I had R&D mode enabled on my 770 for at least half of its time with me (since end of 2005) and did not notice any difference except easier poweron, green texts about system version and 'sudo gainroot' working.

It sounds like an interaction between a bad battery and Nokia's not-very-robust battery/charger firmware. A bad battery could easily appear to charge fully, but then lose voltage very quickly when you try to turn the device on, aborting the power-on sequence. Given a few minutes to settle down after charging, the battery recovers enough to operate normally. Faults like this are all too common with batteries, and the firmware should be robust enough to deal with it.

I don't know anything about R&D mode, or how to get into it. Can you point me?

I just got my N800 yesterday. I don't know if my power on problem is the same, but in my case it's only hard to power on when I have the Nokia supplied mini-SD card installed. It doesn't matter which slot.
As soon as I take the card out. It boots up fine.

I'm going to get another card and try it but I'm wondering if there is either a bad batch of Nokia mini-SD cards out there or a bad batch of adapters.

N800Canada, I am having the exact same problem you are having. I got my N800 yesterday from dell. After I charged the battery and made sure it was full, I installed the nokia update for OS2008. I did not put the sd card in before I updated the software. The computer I used to install the update is running windows vista. I noticed yesterday, after I put the SD card in (the nokia supplied card and adapter) that the N800 would not come back on. I took the battery out, put it back in, and then it powered up normally. As I used different applications, the N800 would lock up randomly. I then took the SD card out, everything worked fine; no lockups, N800 turns on normally.
To get to the point, my N800 is completely fine as long as there is no SD card in either slot. Once the Nokia SD card is in either slot, the N800 running OS2008 becomes unstable, hangs often, and will not power back on after shutdown until the battery is removed. I have other mini SD cards and tried them all with the same result, so I don't think it's the cards. Anybody have a cure? I've been searching forums all day...
Thanks!