>>partly fishing:
>>client and server set to identical locale ?
>
>Could you elaborate more on the topic?

many languages have their own special characters - in german äöüß,
which are running fine when the machine is set to run under the locale for that country.

Problems come up when running on a machine set up for a different country/language.
Back in WinDOS days we had a special routine normalizing strings:
when some special characters were inside it, a form with asked for OS string and our
"fix" was shown, explaining that our software allowed only ASCII OS strings.

I kept this practice, dunno if it is still needed, but might give you another item to test for