When I make a box(static object) and apply a material all is well.
When I Make a Geometry, convert it into a static, then apply the same material too it the material is too dark.
Go into the static mesh editor, try upping the lightmap resolution. When you convert from BSP, it is some very low value like 4 if I remember correctly.
Since converting BSP into a static does not autogenerate a proper UV map, check out channel 1 and if it is good you may want to change the lightmap index to 1.