I think the problem is that inline PGP does not support "foreign" character sets. Have you tried enabling PGP/MIME? This should work as it creates an html mail and sends it signed or encrypted as a file rather than as "scrambled text"
Mozilla Thunderbird 2.0, Enigmail 0.95.5, GnuPG 1.4.8-MobilityEmail
OpenPGP Key ID 0x37858A47