When ever I am doing quest to help neeshka or just doing the main quest to get into blacklake, for the docks alley quest, the game crashes when I exit from merchant quarter or entering merchant quarter(also playing the official campaign), i recently did a fresh install with the GOG version of the game, that i just bought from the GOG store today,i tried all kinds of ways to try to fix the game but no luck,iam using windows 7 64 bit OS,so any help is appreciated.

iam not using any mods or hak files in the hak folder,game was freshly installed today

my card is a AMD Radeon HD 6900 Series