Some of the keys on my toshiba laptop keyboard is not working...

Hello,

hi I have a problem with the keyboard on my laptop, my laptop is Toshiba satellite P855,
well anyways some of the key on my keyboard is not working but if I use a USB keyboard its working fine all of the keys are working. but if I use the keyboard on my laptop some of the letters are not working at all..
the keys that are not working on my laptop keyboard are A,B,N,\,7,left Shift,both Enter. I'm using my USB keyboard right now, I already tried some solution on the internet like doing the system restore, reinstall the driver, clean the keyboard but the same keys that's not working is still not working at all.
please I'll be very glad for any kind of help from you guys.. I'll be waiting for your reply.. thanks..