Ok, so i had my phone on my bedside table - I wasn't even touching it, and it all of a sudden randomly starts to reboot (it would vibrate and bring up the 'NOKIA' screen continuously and in quick succession.

It did this quite a few times before I noticed it and then went black. When I tried to turn my phone on the 'NOKIA' screen would come on and then the pixles would all change colours like the LCD is broken or something and then turn off over and over again.

I took out the battery and waited a bit and then put it back in and now it won't turn on at all! No vibration or anything; dead.

Plugging it in to the computer does nothing, the orange light will either not come on at all or come on and stay on without blinking, but it's not charging. The screen does not turn on, even if I hold down the power button. Sometimes it pulses with concurrent vibrations when plugged it. I've tried holding 'u' down and plugging it in, but nothing happens.

With it unplugged and with the battery in it sometimes just constantly vibrates without pause with the screen off.

Plugging it in with a wall charger also does absolutely nothing. Sometimes it vibrates for like half a second but the screen doesn't turn on or anything, and the orange light just stays on for a bit and doesn't blink still with the screen off.

It's like it's haunted! Help? I bought it from PriceUSA and got it shipped to Australia cause it's not out here yet, and I have return insurance, but don't want to have to be without a phone while it gets fixed if I have to send it back.

What can I do?

EDIT: Ok, I have it on the wall charger and the 'NOKIA' screen came up for a second and then the weird coloured lines and pixles came up and then the screen turned off and I still can't boot it...

Check batery. May be "lost" usb port. It's common problem N900.Try charge batery in other device and after them check in your N900.

i agree, fully charge youre battery then do a reflash

Sounds very much a battery problem possible with a detached usb port, i certainly hope its just the battery or you have no choice but to take it to nokia care.
What was the very last thing you did with your N900 prior to this problem?

Hmm I don't know anyone with a phone with the same battery as mine so I can't get them to put it in their phone to charge. I'll leave it on the charger overnight to see if it charges. The USB port seems fine to me, not loose or anything so I don't think it's that...

God I really hope that it's fine and I don't have to send it back

Any other suggestions?

The last thing I did with the phone was just use it normally, I didn't install anything or change anything.

EDIT: The orange light stays on when it's plugged in (not blinking, just on) and even when I take the battery out it's still on.

So weird...

You must find a way to charge your battery because to finally realise what is wrong will need at the very least a charged battery, if you have a mobile shop near you then get them to charge battery at the very least, i know from my N900 you can plug the usb in and it can take a few minutes for the charge to start being recognised on a flat flat battery.
If your in doubt then take it to your nearest Nokia care centre because even if they dont have the N900's in aussie they will have an engineers flow chart to find out the problem. Sorry all i can suggest GOOD LUCK ok.

I'll try, maybe I'll go to a phone store and try and get them to charge it...

Thanks for your help, and I'll post an update when it's charged.

EDIT: I've had it on the charger overnight and it still won't turn on.

I have a similar (but perhaps not identical) problem. The last couple of days it seems that plugging my N900 into the wall charger hasn't worked properly, and tonight I caught it in the act! It started charging for maybe 5 minutes and then stopped, sending me a message along the lines of "unplug charger to save electricity" and then wouldn't start charging again no matter how many times I removed the battery and SIM card etc etc.

It's off to the store tomorrow to see what they suggest, but I'm not hugely optimistic at this point

Will it go into update mode while pressing U on the phones keyboard and plugging it into your comuters USB port?

No the computer won't even recognize it and the phone won't even turn on.