as an update im sending it back for warranty replacement, thanks lunat for your help and advice, I wish i had paid more attention to what you were saying and didnt listen to robbiethefirst.
Robbie after following your suggestions now i have a phone which has every chance of being denied warranty repair. I appreciate that was not your fault or intention, it was my choice to experiment with your backup menu and flashable images, but i don't understand why you stopped participating in this thread as suddenly as you did, leaving me pretty much stranded with little knowledge or understanding how to proceed. It is pretty ****ing rude actually and i wish you had said nothing at all.
If i figure out a way to flash it back to normal in next 24 hours i'll post it, otherwise just have to leave this unresolved, will edit 1st post so is summary of thread with lessons learnd etc.

Sorry for late update.
phone was returned fixed, but by 3rd party repairer not nokia. Was paid for by phone supplier. Worked for many months.
Recently I plugged into cheap car charger and now I have same problem, have contacted the company that supplied the phone and they have said they will try to get details of the repair for me. Have done a lot of reading and this is a common problem, with a variety of reasons and fixes. I will also try purchasing a new battery and wall charger, although when i sent the phone back for repair i did not send the battery because of postal restrictions and it is still the original battery from the original fault.
Hopefully details from the repair company will provide some accurate information on cause and fix of this problem.

I have a similar problem. Have you tried to boot in R&D mode?
My n900 starts up in that mode but it doesn't charge the battery because that mode doesn't supports battery charging...
Please post any news! This is the thread someone initiated while ago and now I'm writing: http://talk.maemo.org/showthread.php...82#post1047282

here is the thread at nokia support: http://discussions.nokia.com.au/t5/M...1051551#M26012
one of the posters there suggests nokia have a different method of flashing or something (at least, i think that is what is implied), maybe a serial cold flash or something, but i do not know. I will ask him to post details here, because the nokia forum rules prevent him telling me anything more.

Another flash method can be performed using pins under battery - without actual battery - but i doubt it results in different outcome. AFAIK it uses USB D+/D- pins from beneath battery - only difference there is that they're connected directly to chip, without protection circuit (so no wrong polarity protection, no static protection, no any protection - still, nothing that could result in "better" flash than with normal USB).

I guess the best thing to do is wait for details of the repair to come through. It is hard not to blame the car charger for the problem, both times it has been from starting the car with phone plugged into charger. It is encouraging that the phone has been fixed before though.

Oh, battery is now flat, and plugging into charger results in a very quick reboot, so I doubt I will be able to flash or connect to laptop.

You can always charge battery externally.

You could also use a nokia X6, 5800 (i think others xm models work) or C3 to charge the battery.

thanks quokka for keeping us in the loop.

Thanks for advice people. I am going to buy a cheap wall charger with dock and some batteries recommended by dr frost, and wait for details to come though from repair company.

expect an update as late as 6 weeks away, or as soon as tommorow ;P, depending when portagadgets get back to me. It has been over three weeks since they said they would try to get details of the repair. I feel I have some leverage, because the product information provided by portagadgets says I have a manufacturer warranty, but nokia have no knowledge of any repairs being done by them to my device (meaning, a third party did the repair). Personally I am easy, I would just like a fix.