Large Flashlight Related FPS Drop

I know two other people with this problem in their maps and I want to know how to fix it.

Basically, the FPS is nice and smooth… Though when you turn on your flashlight, the FPS drops sometimes as much as 30 FPS.

Turn off dynamic shadows. It’s not your map. It’s your GPU being unable to process dynamic shadows smoothly.

My computer is fine:
Intel Core 2 Duo E7500 2.9 GHz
Radeon HD 4770
4 GB DDR2 RAM
500 GB Sata Hard Drive

Should be fine for source… Anyways, I do not get this on other maps, only the more complex ones that I and other decent-though-not-professional mappers that I know create.

Flashlights are highly intensive, due to their dynamicness.