some keys of my keyboard sometimes work, other times not

Hi.

I have a Pavilion g6 / Windows 8.1

Here is my problem:

some keys of my keyboard sometimes work, other times not (more precisely, the ones of the last line: Z X C V B N M).

When this happes, I go to DEVICE MANAGER, I click on KEYBOARDS and then on UNINSTALL.

When I restart the PC, the keyboard works properly.

But then, at the end of the day, the problem occurs again, and I have to do the procedure described above once again!

Any help/suggestion would be much appreciated.

Thanks.

Francesco