Maybee in the installer ramdisk is a module missing. I know that usual AT/PS2 and usb keyboards are working. Try to use an usb keyboard to install and hope that the full installation will detect the keyboard.
That was one of the things I was thinking about, too. Thanks for the suggestions I will do it: However, I noticed that the keyboard works well on the boot screen:
In the bootmenu the keyboard is handled by the bios so this should always work. But after this it start the linux kernel and need drivers but imho linux has drivers for nearly all keyboards.