Key press interruption

When playing WOW I press "w" to move forward.
I was able to continue forward by holding down "w" and tapping keys to strafe, attack, jump, etc. Now when I hold down "w" to run and hit another key I stop even though I am still holding down "w". I have to release "w" and hit it again to move. This means I cannot keep running while jumping or any other action.
What changed?
I assume it is a Windows thing, but cannot find any info on it.

 

I have posted on a few forums, no help at all. But at least I found out the key press problems are a Windows thing. Usually they are related to changing keyboards or regional settings.
I found many users suffering with the sudden stops in running with the W key in WOW and UT 2003. I assume that would be the case in other games as well.
Most people that @solved@ the problem reinstalled XP. Those @ symbols are what I get for quotes now days. Just another indication that XP is not getting what I want from the keypresses.
I reinstalled keyboard drivers, tried 3 different keyboards, tried UK English regional settings and returned to my original with no change.