Laptop Keyboard Specific Buttons Not Working?

[claustrophobist]

I have a Toshiba L750D which suddenly developed a problem where the entire F1-F3 down to x-c row/column of keys does not work at all, not on BIOS, or on Windows or on any rescue environment or Linux from usb media.

I thought it was the keyboard. So I bought a new one and replaced it. The same problem persisted. Also, the old keyboard worked fine on another similar Toshiba laptop.

So I bought a new motherboard. Aside from a host of new problems (unbootable system probably due to hardware configuration), the problem eerily persists and I still do not see function from the same keys on BIOS, Puppy Linux, or the Windows rescue environment.

I can't think of any apparent reason for the problem. Anyone has any ideas? I don't think the hardware configuration matter, as the problem persists even on another motherboard or keyboard.

I'm completely baffled.

 

[claustrophobist]

I think I have narrowed down the problem. It seems to be some sort of electrical interference. If I remove stuff like the touchpad from the connector, or do no screw everything back together and simply connect the keyboard, it may occasionally start working again - or different rows of keys may become unusable. It is such a weird problem. Any ideas anyone?