Some areas of the game have a player keylight, instead of a global light source. This is mostly for spaces that are meant to be caves (such as Moria and Gundabad) or dark forests (such as Eryn Lasgalen). In these spaces, the keylight is part of a dayfile and cannot be toggled on or off like the personal torch (F10) can be. In addition to this, there is the player-adjustable gamma settings which can bright a space on its own as well.

Since what you are reporting appears to be more of an issue with specific textures and not the scene on a whole, I'd suggest filing a bug on the location. It is likely that the texture needs to have its diffuse and/or gloss channels adjusted.