Alienware 17 R3 Keyboard not working

Hi,

I bought my Alienware 17 R3 (Windows 10) a few months ago and over the last couple of weeks I've had keys randomly stop responding in certain situations.  The login screen often doesn't accept the 'A', 'V','B' or 'N' keys for instance. I've also had these keys not work in Firefox.  If I keep one of the unresponsive keys held down for a few seconds it'll sometimes respond. 

Has anyone come across this problem before? I've tried the unresponsive keys in the BIOS and they seem fine but the problem is intermittent so it's hard to tell if it is a hardware problem.

thanks,

L.