I've looked at the font issue, but the problem still remains unsolved. As far as I can see the Oracle NLS_LANG key is correctly set up.
What I find strange, is that other people have installed the oracle 10201 client (win32) and upgraded their PL/SQL developer without the same problems as I've encountered.
I've uninstalled both the client and PL/SQL D., installed them again, and tried several combinations, but no luck so far.
Since I don't know how any of my action will affect the "production" data, I'm a bit reluctant in just ignoring the "error".
I'm hoping that there is a solution out there.
best regards
Jarle