Thanks for all suggestions but still no resolution to the problem.

@Yomgui
"boot cd" in OF prompts gets appended with "load-size=0 adler32=1" and returns "LOAD-SIZE is too small".
I'll try another bootable CD but the drive works i.e. CD gets mounted in MOS 2.5 and I can read all the contents.

From what I understand the boot image for Mac Mini is "boot.img" and other two - "bootefika.img" and "bootpeg1.img" - are for EFIKA and Pegasos. No?

@Ruud & @bigfoot
Unplugging mouse makes no difference.

The annoying thing is that Mini always spits out CD on startup and I can't remember that it is a normal behaviour.