Bugged lights/shadows

[neiionyc 0]

Ok so, since 1.7.1.2 many times this has appeared on my screen:

http://img861.imageshack.us/img861/4872/shadowjco.png

Its appreciable in the left side of the hospital, but can happen much bigger and disturb a lot.

My settings are :

textures > normal

postprocesing > off

video memory > normal

vsync > off (tested with it on, and its the same)

anisotropic filter > low

anti-aliasing > Off

terrain details > low

objects > low

shadows > off

dynamic range > normal

My graphic card is 9600 gt > runs the game perfect, no fps lag, no problems, it just started in the last updates :(

Any ideas? Thank you!

pd: i have been playing since May and this never happened before