same happened to my nokia n900 last month. just like u stated .It stopped charging, starting n there was only yellow led flashing .

That yellow led , it started to flash for some time and stopped and then when i tried to start d device there was nokia screen and sometimes u-boot menu, both without backlight.

I tried many options and luckily one worked.
What i did is simply connected my device to my laptop and left it for 10 minutes and pressed that power button long enough untill i saw that clear bright u-boot menu appearing infront of me. I tried this thrice. I was convinced that the device was bricked. Sorry for the bad english.

hope this helps.