Nailed it. Ensuring heap_form_tuple was properly defined resolved the issue.
Thanks a lot. Without your help, I would probably have spent more time looking at the 32 <=> 64 bit thing first, since I was pretty certain that we had this warning in the old compile. I suspect I am wrong about that, though, and that the actual problem is the heap_form_tuple declaration being relocated, as you suggest. In either case, going through the code and ensuring that we had that include everywhere in the code seems to have cleared up the problems (all tests running OK).
Regards,
Michael A.