Hi,
I think something has gone wrong with my board.
When i try power it up from USB, it turns on and when - i guess - the bootloader loads, it powers off....them LEDs on board sort off fade out as if it is losing power and then dies. I tried powering it with the Vin but doesn't want to power on...
I was on the brink of completing my project and this happens - is there any other way i can boot it??
It sounds like you have a short circuit on the board. There should be a temperature sensitive polyfuse on the underside of the board near the USB plug... see if that is getting warm.
I had this happen once where the polarity protection diode failed and as a result.. neither power source would work right and it appeared like a short across the supply. Too little information to really give you an answer...