Keyboard recognized only at first boot

Hi everyone, yesterday I built new pc for my brother and encountered a problem.



When I start pc first time (after reconnecting it to power socket), Lenovo Y Series Y730 Keyboard Replacement Brand New US Layout is recognized and I can see HID Keyboard Device and Standart PS/2 Keyboard in my device manager, but when I restart or shutdown and again start computer, I see only HID Keyboard Device and I also can't use keyboard, it seems like frozen. Num Lock is on, but I can't turn it off and no keys are working.



I am also able to enter bios when keyboard is not recognized, but I can't use it when I'm in bios.

On first boot I can use it in bios.



I noticed that on first boot, when Lenovo Y Series Y730 Keyboard Replacement Brand New US Layout

is recognized, all three lights (num lock, caps lock and scroll lock) are blinking two times: when bios screen is shown and after windows boot screen. When it is not recognized, I don't see second blinking after windows boot screen.



Can anyone help me? It's very annoying problem. Now I am on first boot and able to use keyboard, but if I restart, Lenovo Y Series Y730 Keyboard Replacement Brand New US Layout becomes useless.



Operating system is Windows 7 Ultimate x86.

Hardware:

Motherboard: Gigabyte GA-78LMT-S2P (updated bios to F5a)

CPU: AMD Athlon II X2 260 3.3Ghz

RAM: Crucial Rendition 2GB DDR3 1600Mhz

Video Card: Gigabyte HD6670 1GB DDR3

PSU: FSP Hexa 400W