dot plt files question

[Francisco Solsona <solsona@acm.org>]

Hi all,

I create a ".plt" file using the `pack' procedure (from pack.ss), and
everything goes fine until I try to unpack it, it says something like:

,--------------------
| setup-plt: Unpacking SchemeQL from schemeql.plt
| expected a unit, got #t
`--------------------

Is there any way to pack a module?  Do I need to have a signed unit? 
(And yes, I did read the `pack' section in setup/doc.txt =)

Thanks,
--Francisco