This is a bug i'v seen many times sometimes others also where effected by this.
I do not have any snapshots any more only the details in wich it occurs.
Basicly sometimes lighteffects seriously screw up for some reason and I wasn't the only one troubled by it.
Basicly a normal light effect suddenly turns into a "red" flashing squared figure. With random holes in the middle.
Times in wich it occured to me:
-When updating a level this bug sometimes happens
-When reconnecting after being dced (rare..)
I tought it might have had something to do with either mine or other people's graphic card or might be a general bug that seldomly occurs. I do not have any technical details nor usefull data/snapshots on hand. But if anybody else has had the same problem it might be worth checking into.