are you sure these keys aren't literally sticky?
you could try adjusting the
Code:
Option "AutoRepeat" "500 30"
line in your xorg.conf, that will at least slow down the repeat key hits. I believe the first number is the delay (in ms) before the repeating starts, and the second number is the rate of repeat.
come to think of it, commenting out that line altogether might help. However, I believe KDE sets keyboard autorepeat itself, regardless of what it says in xorg.conf. in control centre, under peripherals-->keyboard you can find the KDE settings for autorepeat. I can't comment on how Gnome deals with this.
I'm willing to bet there's some goo under your tab and arrow keys though - autorepeat stops working once you press another key, even if you keep holding down the original key.