I have a suggestion, try using gi_joe, make the skylight a .1 intensity and make the ground intensity .05. If you're trying to use a scene where it's really bright, try using a point lightwith gi_joe. Give the point light ray traced shadows. if it's not really bright, you want to use a depth map shadow with a dbias around 6 with a resolution of around 2000-ish. That migh get you started. Try messing around a little bit. I use 64 lights for my skylight and 16 for the ground. hope this helps,
btw this is really only good for outdoor lighting, for ondoor lighting, i try to stick with 3 pt. lighting.