Boot problem AGAIN!

I know that many similar question have been posted here but none seem to
apply to my specific problem. I have installed QNXRTP to a separate hard
drive (hd2) and it shows there as partition 3. I also have System Commander
2000 to boot multiple OS’s, which correctly recognizes QNX system on hd2.
When I boot QNX using boot diskette everything works fine (apart from a
message “Reserved RMEM failed”).
However if I try to boot using System Commander I get a message “Press…”,
then two rows of dots ending with letter C. Then the boot hangs. I have
disassembled the QNX boot record on absolute sector 63 and indeed there is a
subroutine which ends in an endless loop just before sending a “C” to the
screen unless AX register contains value less than 400Hex. Unfortunately I
could not disassemble the boot diskette since my dissembler does not
recognize its format. Any suggestion what to try next would be much