Sporadically erroneous keystroke repetitions

[Oliver Block]

Hi,

I sporadically encounter repetitions of my keystrokes. What happens is
the following:

I press any key, say "a", and instead of getting just one "a" I get many.
Not just a few but it is like if I would keep pressing the key. Then I
have problems stopping this. Often it does not stop itself.  I cannot
tell what I have done exactly in these situations, but normally I tried
to press other keys to make this stopping. I guess I often used Esc.
Then normally it stops and afterwards everything is fine. But
this happens quite regularly (once every few hours) and it is very
annoying. This behaviour is somewhat new (since a few month). I am not
sure, but maybe it started after switching from a Ubuntu system to
Debian lenny now. The installed xorg has version 1:7.3+20.

Sometimes (less often) something else happens. In this situation it
seems that some modifier key (is this the right expression for the keys
like Shift, Alt, Ctrl, Caps, ... ?) is pressed (but there is none
pressed). Once it was like if Caps would have been activated. Other
times like if AltGr would be pressed.

I am not sure if this is a hardware or a software problem and where it
might be located.

Any hints?

Best regards,
Oliver