Booting from 64G microdisk in Blackberry Z10 phone

Up until a Blackberry upgrade I was booting amazingly and efficiently from a 64G microdrive in a Blackberry Z10 phone recognised a a remore USB device.
Now, following a BB OS upgrade (that I wouldn't have expected to compromise anything at all) the boot/syslinux/syslinux.cfg is definitely picked up (because I get my own recognisable boot prompt) but in searching for the KNOPPIX/KNOPPIX file to get going, all that is searched is sda1/2/3 and sdb1 (i.e. the microdrive) is never located and after a few repeats I end up with the dreaded
Could not mount disk to /mnt-system
sh: can't access tty; job control turned off
I really cannot tell what has changed, or why. But clearly it has, and with these devastating consequences: it doen't work.
Is there a cure e.g. (but not necessarily) a way I can direct the boot sequence to /dev/sdb1? (Not ideal: hooked up to a different machine, it might be something different).
NB This is NOT knoppix.iso I am pointing at. The iso has been unziped onto the microdrive.
Very hopeful that you can help. This was the most perfect portable system. Just my phone!! No sticks, no CDs ...
fergus

You may have to use the boot parameter knoppixdir, even though the Knoppix kernel should look for KNOPPIX in /KNOPPIX/ on all the media, including /dev/sdb1.

I have syslinux in /boot/syslinux/ and all the Knoppix files in /knop720/ . My entry in syslinux.cfg is

Code:

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LABEL Knoppix
MENU LABEL Knoppix 7.2.0 32bit on this boot medium in /knop720
KERNEL    ../../knop720/linux
INITRD    ../../knop720/minirt.gz
APPEND    knoppix_dir=knop720 lang=en apm=power-off nomce libata.force=noncq hpsa.hpsa_allow_any=1 loglevel=1 tz=Europe/Copenhagen keyboard=dk xkeyboard=dk no3d

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Can you put the microdisk in another computer and check the file system integrity and check if all files are intact ?