I am having problems to install Debian on my Macintosh Cube (800Mhz)

There is another problem with Debian Linux on my mac, but I thought it
is better have an extra posting for it.

I had a Debian installation before, but I was not realy lucky with it.
It happened sometimes that after booting the keyboard refused to work. I
could not even type the password, only the mouse could be operated, so I
was able to reboot the computer. For the new boot I typed the start
parameter "old", and then I could access my computer. One of the next
boot procedures the parameter "old" did not let me acces the computer,
then without any parameter I could boot Debian.

Recently I re-organized my harddisk, and I decided for a new Debian
installation as well. I got me 3.1r4. But I encountered the same problem
with a non-reacting keyboard.

By the way, it is a USB-keyboard.

Also times ago I started a Knoppix Linux, and that time I had no working
keyboard either.

Can anyone help to find a solution?