When I have the keyboard repeat feature enabled under KDE, my keyboard sometimes will act as if a key is stuck and it will repeat that character for a while and then stop. This happens intermittently, but when it starts happening, it does it for like 10 seconds, then normal, then 10 seconds again, then normal, etc etc.

It makes it impossible to use the keyboard while the repeat feature is turned on.

It will stop doing it altogether if I just disable the feature, but then I have to manually press a key if I want it to be used continuously (like the backspace key).

The repeat feature works normally with no problems at init 3. The problem seems to happen while in X only.

Has anyone experienced this and know how to fix it?

I have almost the exact same problem. On my laptop the last key pressed and released will occassionally repeat forever until I press any keyyyyyyyyyyy. (yes, like that) Very annoying, especially if the key is delete! I've been trying to sort this out for a while (months) now. I hope it's not a hardware failure but some configuration issue in X or the kernel, however I do not know the answer yet. One hint: I see kernel messages like:
atkbd.c: Unknown key released (translated set 2, code 0xe0 on isa0060/serio0).
that seem to be correlated with this. Fixes I'veeeeeeee (argh!) read about for similar problems on Toshiba laptops (re: psmouse rate) do not solve the problem.

I don't think it's a hardware problem because I tried 2 different keyboards from 2 different manufacturers and they both have the same problem. I believe it may have something to do with the USB controller and driver compatibility. Now what I can't understand is why this only happens in X, and not in Init 3.