Fsx and 8 Cores : No go

Hello, I just want to inform you that Fsx Sp1 isn't working properly with a 8 cores computer. Sometimes it works, but usually "freeze" when I load a saved flight. If I set the affinity mask to use only 4 cores, it's OKHardware :MB Tyan S2696Cpu : 2 x Xeon E5345 (quad)Geforce 8800GTSRegards,