In the past, there was an issue with when after loading a map, it would be very dark. Something with the lighting of the map or something. Normally it was fixed but logging off, logging in again, possibly taking up to a few times to do this. Also, I remember that for certain maps, like the old Oja road map, that simply waiting until the in game clock changed would fix it. The reason being, the amount of light would change with the in game hour, to provide a bit more realism. Whn the game changed the amount of light, it would set the light to what it should be, hense no more complete darkness. I'm not sure if the DR is set up like that though, so that option may not be feasible.
If push comes to shove, you can turn fulbright on, to get yourself out of the DR. I'm not sure if the devs had thought the y squashed the darknes bug or not.