You need to check all the standard stuff: disable all add-ons (via the control panel), test on the default style, and (in this case), test with the default (English) language. If any of those steps fixes it, you need to identify which element is the cause and resolve it there.
It might come from your php installation. You should contact your host and ask him to check if your PCRE supports utf8 characters.
Check this post and this demo (from the post). You might also check this.