Bottom row on the internal keyboard - "z" to "." not working

Hello everyone. Recently i got this MacBook Pro from ebay and it said that the internal keyboard in not working properly. There were no info on whether there was a spill or not, but everything else on the notebook is working. The keyboard row from "z" to "." wasn't working. I made all kind of resets - smc reset, pram reset. Changer the ram. Fixed the hard disk permissions. Formatted the HD and installed a new OS. No change. I purchased a new keyboard, installed it and the problem still persists. Like nothing changed. The logic board keyboard slot doesn't show signs of problems, and the keyboard i installed is new, but the problem stays. The model is Late 2008 Macbook Pro A1286 2.4 core 2 duo. It is the UK layout. Strange thing happens when i press 3 keys together. On the uk internal keyboard - it's the 3 keys right to the left shift - the "`", the "z" and the "x" - the volume goes up - as if i press the volume up key (F12). Any ideas ...

I don't know what to do next.