Guys another thing to try is this...
after getting the coloured lines with fully charged 2100 NiMh batteries, I thought something was dodgy. Opening the battery cover and rolling the batteries slightly, made the unit boot. It would seem that the battery holders, or the battery terminals are coated in a very fine residue / film. Try roughing them slightly with sandpaper or a blade of sorts, just to remove anything that might cause a poor contact. Usual disclaimer...
I am not responsible for your actions should you damage anything.