Problem with Asrock P55 Deluxe3

[Flanker-B]

I've recently bought this mobo to replace my p55 pro/usb3.
On this "new" mobo my graphics card works on 8x pci express speed instead of 16x. I only have one graphics card (Gigabyte GTX 460 OC 768MB).
Please help.
Could the problem be in my psu (LC Power Silent Giant Green Power 650 W bronze 80)?