It looks a bit like this bug from the PGP faq
<http://www.cam.ac.uk.pgp.net/pgpnet/pgp-faq/faq.html#AEN1096>:
The initial release of PGP 2.6.2i contained a bug related to
clearsigned messages; signed messages containing international
characters would always fail. For that reason, it was immediately
pulled from distribution and re-released later, minus the bug.
If you have problems with 2.6.2i, make sure you downloaded your
copy after 7 May 1995.
Ciao. Vincent.