If you have a white light with a large range in your level then dynamic entity's (characters,weapons,doors etc) may be taking their lighting values from it, even if its in a corridor far off.
Before getting too complicated test the character by creating a small 5x5 floor and placing a single light with a small range next to it, you can mess around with a few lights and see what works best to get an idea of how to light levels to suit dynamic entity's you are using..
If you still have problems then its a shader issue but I doubt it as you say the weapon has same problem.
Its also a good idea to place a segment outside your level to force FPSC to rebuild lighting when testing this, you can remove this or move it around for each test.
I don't trip over...I do random gravity checks.