PGP verification fails if there is an attachment

[Merciadri Luca]

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Hash: SHA1

Hello,

When attaching some file to one of my outgoing e-mails, the receiver
receives the mail correctly, but my PGP signature is altered, as he
receives the warning "PGP signature check failed." I tested in an e-mail I
sent to me, using Thunderbird for fetching, and I encounter the
following messages:

gpg invalid clash escaped line --=-=-=\n
(two times)
gpg Signature made ... using DSA key ...
gpg BAD signature from 'Merciadri Luca'

This seems linked to my signature problem, doesn't it?

Any solution would be much appreciated.
- -- 
Merciadri Luca
See http://www.student.montefiore.ulg.ac.be/~merciadri/
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Version: GnuPG v1.4.9 (GNU/Linux)
Comment: Processed by Mailcrypt 3.5.8 <http://mailcrypt.sourceforge.net/>

iEYEARECAAYFAkqzbeEACgkQM0LLzLt8MhzrGACeM6Ydxx4hOoQ4B3Sh4DhMIHDS
Xd8AoJbg8ISez553kEHgb+0riNjqqtck
=ELIs
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