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Is it completely dark or does it look like it is in the underground or cave mode? Try pressing the u button. I got this information from here. Thanks to Starmon8472.
If you've tried a force update and/or the basic troubleshooting guide then I'd suggest try allocating more RAM if possible or try another minimap. Minimaps are client side and are not needed to connect to a server if that is what you are trying to do. Mapwriter or opis if I recall correctly requires a lot more resources than the other ones like Zan's or Rei's. So for those you can pick and choose.
All of them are black? That points to a client/hardware possible problem. I cannot remember, but if you are using 64bit if you are have you tried the arguments here for better performance?