When you say you have a lot of lights around the map do you mean in the same area? I know there's a bug where if a face is receiving to many lights it turns black.

Can you provide a screenshot of those same areas but in hammer?

This happens with interactive lights.

As soon as you give a light a name, it becomes an edict, and the engine therefore creates 2 versions of the lightmap, one with the light on, and one with the light off.

Any surface can only have up to 4 different light styles on it.

Solution : Do not name your lights, unless you require them to be turned off.

If you do, name all the lights that turn off simultaenously with the same name, so that the engine will merge them in one light style.

Giving a light an "Appearance", like Blinking and Flickering, does the same thing.

Secondary Solution : Reduce the light map scale on the affected surfaces to reduce the artifacts.