[AS] Problem with non English characters in file path

I wrote a script that exports a pdf file from ID, rasterizes it in PS, applies an action, saves it as another pdf file, and finally creates a Mail message, and attaches the file to it (the last part is written in AppleScript).

The problem is that it doesn't work when the path to this file contains non English characters.

This works:

make new attachment with properties {file name:"/Volumes/Macintosh HD/BackUp Tetard/Test.pdf"}

but this doesn't:

make new attachment with properties {file name:"/Volumes/Macintosh HD/BackUp Têtard /Test.pdf"}

I remember vaguely that I read somewhere that AppleScript can work with Unicode — in other words with such characters — starting from some version, don't remember which exactly, but it seems to me — Leopard.

I am on Mac OS X 10.4.11 right now. Will updating solve this problem? Does anybody know any solution to this problem: a scripting addition, some hidden setting, etc.

I made a little test: used a Russian character — ё and it works, but when I use — ê (Dutch) it doesn't. May it have something to do with the Region setting in International panel?

Thanks in advance,

Kasyan