Multiple Dynamic Lights in a zone possible?

Has anyone managed to get two dynamic lights working in 1 interior zone at the same time? Whenever I add my first light into a .dif zone it works great, but as soon as I add a second light, or a third light, the new lights don't seem to work. And as soon as I delete all other lights in the zone except for one, the light will work. Is it a limitation of the engine that I can only have 1 dynamic light per zone? Or am I doing something wrong? Thanks!