strange graphics problem

some advertising boards (i.e.the orange ones that are below the stands at interlagos and imola overhead i think bridgestone just past the hairpin to name just a few) and crowd textures mainly at hockenheim and imola flicker a lot.im sure ive read a fix for this before but cannot find using search.i could understand it if it was quite a distance away,but the adverts do it when driving quite close to them,other than that the game runs fine using geoforce ti4200 and amd2000+.