I think we can agree that what Marty is trying to do should work - but something fundamental is getting in the way.

Maybe it is your prom bootloader - It may not like gaps in the hex file data! How can we prove this? Write a program that does a hex dump of the code space and see where your strings turn up (if in fact they do appear!). This will prove/disprove that your strings are where you want them to be. If the strings do appear where you expect them to be, then you will have to come up with another hypothesis and a test to prove/disprove.