Too many light styles on a face
Just the normal field rotated 90 degrees, isn't it?
Mevious, I learnt that from Tophattwaffle and I'm sure I'm right. Please read this and go to the final epigraph called "Limits". I'd say that your example means 2 light styles...
useful tools and stuff here on TWP 
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At the coordinates specified there is a surface lit by too many "effect" lights. This includes lights that have a name (which compiles both on and off status so you could switch them) or a light using effects like flickering. Remove some of them, disable flickering effects or make sure they don't have a name.
Note: A surface may only be lit by up to 4 lights with different targetnames. This means a face can be lit by unlimited different light styles as long as they share up to 4 names.
Vrad doesn't care what a light style is, it cares about the number of different light states a surface can be in.
Co-operative: Lightspeed Upstairs Downstairs
Deleting the red light didn't fix the problem, going to try removing the laser field completely to see if that helps
No, your problem is the cube_dropper: edit it and remove those lights I mentioned... And don't remember to save it under a different name! 
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Your laser field isn't causing anything, thats just a texture on a brush - it doesn't emit any light. Are you using many different colored lights, or flickering lights in your map?
Ok editing the cube spawners has removed the vast majority of the errors however there are still a couple of places where it seems to be happening, mostly directly underneath a block that I have manipulated with the vertex editor to make it angled.
And no I'm not using any flickering lights in my map, and apart from the red light in the centre of the laser field all are the same colour and brightness.
Edit: The angled surface isn't responsible, tried removing it and still get the same error in the same place
http://www.mediafire.com/?17doi1ituyk999c
Uploaded the VMF, bare in mind this level is incomplete so there are still some items missing from the final chamber, I still intend to add deadly goo and the triggers required to kill the player when falling into the chamber. Also provided the edited cube dropper instances (placed in /sdk_content/maps/instances/gameplay)
Ok I've done a bit more digging and I think i've narrowed the problem down to the laser catcher, I encased it in a nodraw texture and that removed all but 1 of the remaining problems. Are there laser catcher models in the game cache that don't have light effects?
Erm.. prop_laser_catchers don't have any light effects, the ring around them is... I'm not sure what, but I'm pretty sure its a prop with a different skin, and the red light in the middle is a particle system.
I know there are two different laser catcher models, though. Just not sure how to switch between the two.