We've had this issue for a while now and haven't seemed to be able to find a fix. We're currently working with the stock BSP c40. For some reason, without any tag work prior, select dynamic lighting will fail to light the BSP in all scenarios. However this seemingly bad dynamic light still illuminates units as well as scenery items perfectly fine. Roughly half of stock the dynamic lights work. A dynamic light that always manages to stop working for example, among many others; the stock frag grenade flyby light.
This issue seems to occur on any BSP we try. Someone suggested at one point it could be a HEK+ extraction corruption issue, which seemed to fit the issue perfectly, but upon trying another extractor the issue still exists.
I have yet to find someone that doesn't get this issue, however all maps I've seen released don't have the issue, which tells me the problem is occurring in development.
I would go into more details about the issue and the many, many things we've tried over the last 6 months trying to fix it, but this will just turn into a book.

Any ideas?

Make sure you've dynamic lights on in the halo video options?

>.>

They are

Just letting you know I have noticed this on one of my test maps - it doesn't particularly bother me as I'm never releasing it, but I can have a play around and see what might be causing the issue. WIll get back to you on that one.