Grub boot menu keys has suddenly changed, can't use arrow keys

I'm using Kubuntu 12.04, grub 1.99 on an Acer Aspire 5750 laptop, with a multiboot system. Suddenly, I realized I can't select boot option with arrow keys but I can use "p" for previous, "n" for next, and "e" for last option. Extarnal usb keyboard gives the same exact result. I updated grub and checked all computer for malwares, still negative result, no effects at all.
If i boot kubuntu, any kernel version, my keyboard functions properly later on, I can type password in, I can change keyboard layout with ALt+Caps, etc. But if I boot win7, I can't type my password in, not even with on-screen or external keyboard. However, pressing backspace fills with certain (hidden) characters the password field.
I assume a loaded kubuntu kernel uses different drivers for keyboards, but why grub and win7 fails to use theirs?