Portable TB on Wine/Linux

Hi,

I've been using Portable TB 2.* on Linux/Wine, and it worked fine.
After upgrading to 3.1.6, mail texts (text-only, no html) became unreadable.
Not all mails, but a lot of them.
The settings are unchanged and still work on PTB 2.0.0.24.
Folder settings: UTF-8, ISO-8859-1 or ISO-8859-15 set as Standard Encoding, but "Standard ...zuweisen" ( e.g. "apply standard (?)") is not checked.
Usually that works, with the exception of mails with incorrect encoding. But here not only a few special characters are unreadable, but the whole message is scrambled.
Most mails are encoded ISO8859-15 or ISO8859-1 and display correctly in "normal" Thunderbird (Win and Linux) and also Portable TB 2.0.0.24 on wine.
It only seems to be a problem of displaying, since it is possible to copy the mail text into an Editor (kate), where it can be read!
Source code (crtl+U) is completely unreadable, too.
Sometimes it is possible to temporarily achieve a correct display using a wrong encoding like ISO-8859-2 in "Ansicht - Zeichenkodierung".
Enigmail works, but the decrypted output is unreadable, too.

Portable Thunderbird 3.1.6 (german), Wine 1.0 / 1.2, Ubuntu 10.04, Suse 11.2.

Any ideas?

tia, muzel