I had this problem a few years ago

[suber36g]

I been gotten this problem years ago during the spray crisis and I don't how to remove it, it effect the waters, props and the textures flash a lot (when i mean flash, i mean it get a bit brighter but not turn pure white.)

 

[Asd417]

You probably didn't set up the cubemap properly. There are good tutorials here about it.

 

[suber36g]

I mean I had this problem before mapping, beside the purple checkers pattern which only happen when playing TF2 create server for Drainpump. But the purple checker pattern doesn't appeared at all when play the map using the run map in Hammer.