keyboard - Strange experience in my laptop of certain keys not working

I actually asked this in HP support forums and their Customer Service Rep., but no one knows whats going on.So, I am throwing open this question here , esp. so that some Geek Squad guy, who has seen this before can give an insight into what could be happening.
Problem - "b", "n", Caps, "-", ">" (right cursor), "END" group of keys stop working abruptly.

This is a Elitebook 8460p under warranty. Neither me nor the tech. field support is able to figure out what's going. At the outset - If you feel ANY of the above letters missing in the write up, its because I did not, "toggle invoke" my virtual keyboard. I just had the keyboard changed and this problem still persists in fact it has gotten more persistent after the new keyboard change .
Earlier -it was more fluctuant than it is now. My options are to change keyboard, system-board or both. Keyboard change did not help so far. Before I try the system board change I wanted to throw open this problem. I read SIMILAR posts in previous threads on HP support - but NONE of them have been able to identity the root cause -they are in fact all Incomplete, where the last post from the asker still shows no resolution. Did anyone run into the problem and figure out where it hits (software or hardware?). All the diagnostic tests are normal.

I downgraded the keyboard driver but the problem still persists .My best hunch on this is that, one specific strand of connection from the keyboard to the system board isn't working & that maps to this group of keys .It maybe that the corresponding system board connector for this is not working. A hardware key-map document ( which circuit strand maps to which keys ) will confirm this. I have a dual boot environment with Ubuntu & when the problem is present in Windows its also present in Ubuntu. USB keyboard works just fine.

Another observation is that once these set of keys are dead, the keys B or N (think most times it is B) brings back alive this dead bunch, like 50% times (for the rest - I am stuck and have to use a work around).