Hello all, i only made an account to hopefully help others who are having problems. I have the MD90 and the red and blue light were on constantly, i left it charging for 15 hours and nothing happened, light stayed on.
I tried resoldering the battery like suggested on another forum, to no avail.
However, whilst resoldering, i found that the camera lense is mounted on a block that plugs into the circuit board. My lense had come loose so i think the lights were just to show that there was an error. I slotted the lense back in and the camera works perfectly. Make sure you slot it in the correct way around as it is accepted both ways. Or you might, as in my case, have the blue light just staying on, with the camera still locked up.
Hopefully my experience will help someone!
Thanks to cyberknight for his break down of what the lights mean, was a very helpful guide!
Thanks all!