Graphical problems with gecube 3870x2

[CCCP]

My config is phenom 9600, 2 gb ram xp sp1 gecube 3870x2. When I run overture first time there were missing/transparent textures in first level and the game was freezing in the menu but after i patched it to 1.03 menu it was ok and `all` textures come back. But then i saw a small barrel beneath a chair that was that was dissapering and showing as I were moving close to it or turning my wiew in other directions. Then i thought ok one missing barrell isnt problem but later i ecountered other similar problems like some walls missing and stuffs like that. If i could get some tips or suggestions i would be very happy. Im from Croatia so forgive me on my poor language. And i almost forgot to tell that sometimes different textures are missing but barrel on first level is always one of them.PS my driver is newest 8.7