OK, the extra context is making more sense.
Painful though it may be, I'm thinking that the XModem upgrade (which directly replaces the operational code) is the most probable path to resolution. The procedure is documented here:
KB 5605, "
code:Firmware Upgrading a SecureStack via TFTP or XModem
" (
http://gsfn.us/t/49n93).
Also note the additional cautions at the top of that article; in particular, KB 11617, regarding a
possible problem with direct upgrade of 5.00.xx firmware to 5.02 or higher - with a stated solution.