Help with custom properties (or something like that)

[Cubist at aol.com]

   I've run into a weird problem which I can*not*, for the life of me, 
understand or solve. Let me explain, in hopes that *somebody* out there can clue me 
in...

   I'm working with MetaCard 2.4.1, running under MacOS 9.0.2 (it serves my 
needs, what can I say?). I have a stack with a custom property called 
"AdMailTemplate". This property contains a file. I know it's *in* there, because the 
statement "answer the length of (the AdMailTemplate of this stack)" gives me the 
length of the file... but "answer (the AdMailTemplate of this stack)" gives 
me *nothing*.
   I've tried using base64Encode on the file before storing it in the 
property, and base64Decode after retrieving the stored file. This was a partial 
success; "answer (the AdMailTemplate of this stack)" no longer gives me bupkiss, 
but it base64Decodes to nothing.
   What the heck is going on here? Why should a custom property behave like 
that? Is it possible that there's something weird about the content of said 
custom property which MetaCard doesn't like? Would it make any difference if the 
file contains nulls and/or other funky characters? Is it possible that the 
file's bytes have coincidentally copied some portion of the MC2.4.1 stack file 
format?
   I sure hope this is a known flavor of bug with a known solution, that 
someone can say "You need to do X" and it's fixed. If more information is needed, 
I will send a copy of the stack (via private email) to anyone who asks.