Problem interoperating with PGP Univeral?

[Blumenthal, Uri]

I am trying to get cleartext-signed PGP/MIME messages produced by PGP
Universal 2.5.3, verified by email clients (Thunderbird-1.5.0.10 +
Enigmail-0.94.2 + GPG-1.4.7).

So far my experience is:

- Pure plaintext (neither PGP/MIME nor PGP/Partitioned) messages are
verified OK.

- PGP/MIME encrypted and signed messages are decrypted and verified OK.

- PGP/MIME or PGP/Partitioned messages (HTML body and/or attachments)
fail signature verification, with error message from GPG:

  Cleartext signature without data

I've submitted help request to Enigmail list, but perhaps somebody here
can advise me regarding this issue? Maybe there are settings at PGP
Universal that should be changed to make its output "friendlier"? Or
maybe there are GPG setting that would allow verification of those
emails? 

I'll be grateful for any help!

Thank you!
--
Regards,
Uri Blumenthal
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