USB Keyboard not working properly even in the BIOS environment !

Problem Description :

4 Newly bought desktop computers from the same manufacturer came with USB keyboards which don't work properly on any of them (it doesn't take all character presses , sometimes it takes a long press on the character button and sometimes not , you cannot type a full sentence without missing half of the letters) .
The problem appears from early start-up stages of the PC (when I try to enter the BIOS by pressing <delete> , and also when working with the BIOS.

Necessary Data :

1- PCs are all identical .
2-Each PC has the following characteristics :
a-Processor : intel 2.9 GHz dual core G2020
b-RAM : 2 GB
c-HD : 500 GB
d-MB : ASUS H61 M-K >> Motherboards - H61M-K - ASUS
e-OS : Win7 ultimate x32
Experiments done :

1-I tried every keyboard on another old computer and they were all fine.
2-I tried another PS/2 Keyboard on my new PCs and it was fine .
3-I tried another USB keyboard on my new PCs and the problem is still there .
4-I tried to connect each keyboard to every USB port in the computers and the problem still exists.
5-I tried to update BIOS with a newer version from the manufacturer . The problem still there .
6-I tried to format the hard disk and installed a fresh copy of Win7 and reinstalled all driver definitions properly which was done successfully but the problem wasn't solved .
7-I checked <Device Manager> entries one by one and found out that there is no contradiction between drivers , windows says they are all working properly.
8-Mouse, external DVD drive and USB flash disk all work fine using the same USB ports .
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I need you to help me please answering these questions :

1-Can device driver installation inside windows affect performance of the same device inside BIOS ?
2-What could be the cause of this problem and what could be its solution ?


THANK YOU VERY MUCH !

hi, i just had one thought.

go to bios and see if there is usb legacy support if their is enable it.

Thanks for your reply oscer1

I tried that also . Sorry I forgot to mention it .

since these are all new computers see if the manufacture will give you support on the issue. or just use the ps/2 keyboards. how is the onscreen keyboards? maybe its a glitch with the keyboard controller using usb. strange issue.