I don't know if it's a designer problem or extlib problem, but it occurs in ExtLib controls.
In Dojo button control, when we use "Ş" and "Ğ" characters (S with cedilla and G with cedilla, only uppercases) in label, XSP editor crashes. It doesn't matter where these characters are used (in the middle, at the end, so forth). When I investigate the problem further, I saw the same problem happens in all extlib controls that has text-visualization. Ones that I have detected are dojo button, dojo radio, dojo checkbox, Form Table, etc. The problem is also independent from operating system locale.
When you put the following XSP into a custom control and save it;
<?xml version="1.0" encoding="UTF-8"?>
<xp:view xmlns:xp="http://www.ibm.com/xsp/core" xmlns:xe="http://www.ibm.com/xsp/coreex">
<xe:djButton id="djButton1" label="Ş"></xe:djButton>
the custom control can be used without any problem. However, when you try to open it again with XSP editor, XSP editor fails. After its failure, if you try to launch XSP editor again, designer stops responding. I have attached the trace files.
Also, the following screen cast shows how XSP editor fails showing non-us characters:
Errors and traces is in the following link...