Slight keyboard lag?

I have noticed recently especially when on battery the keys don't respond unless I hold them down longer when typing. Not lag as in after I type the letters slowly appear rather a more unresponsive unless held down longer kind of lag.

This is most apparent after running skype or itunes on battery then going on the net to browse.

However this morning it did it even plugged in after cold boot up. Needless to say it is really annoying and I want to fix it. Could it be the memory? When it happens I look up to find letters missing all over the place!

Anyway this problem doesn't happen all the time just sometimes and mainly 95% of occurances on battery.

Any ideas? Memory/CPU? Machine in sig. A reboot fixes it.

 

And if you just type the key and don't hold it down? Mine does that from time to time but it a wireless connection: I type a word, then there's a fraction of a second before it appears on screen. That's only when I begin typing, and after a rest. Once I'm going though, the response is immediate.

 

No the key doesn't respond as if it wasn't touched. No lag. Just unresponsive. To make them resposive you have to hold them down. Odd

 

While this seems like an obvious hardware issue - this could be software/drivers/virus too.