Loosing keyboard events - Please Help!!!

I'm writing a delphi 3 program with a keyboard event handler.
Everything works exactly as expected ... most of the time.....
In normal processing, there is a keydown event, a keyup event and a keypress
I handle most of the keyevents in my keydown event, but some of the
keystrokes like '1' to '9' I handle in the keypress event for simplicity.

Now what happens OCCASIONALLY is that the keyevent handler dismisses some of
the keystrokes.
Sometimes they get to the keydown and sometimes they do not generate any
keyevents at all.

At first we thought it might be a defect keyboard driver or hardware, but if
we switch to e.g. wordpad everything works okey.

All other input devices works fine (mouse input)

Some of the keystrokes is handled okey (and there are no system in what keys
are handle in keydown and in keypress).

If a key stops generating keyevent, it keeps being stopped until the program
is restarted, then it works fine again.

Has anyone ever experienced anything like this??? and it is possible to
definae what the problem is???

I hope anymone can help me, Thanks in advance
Helle Skaaning