By the way:
    I think that something was definitely wrong with installed 
bootstrap. I've copied brand new kernel from CF card to harddisk, and 
still I couldn't boot it. This time it was certainly smaller than 5MB, 
so I decided to reinstall boot loader.

    After starting from CF card and issuing "installboot /dev/rwd0c 
/usr/mdec/bootxx /boot" everything went back to normal. Now I'm able to 
boot NetBSD from internal harddisk.

Greets
Radek Kujawa