Installing and upgrading help

hi U there,
Moodle usually manages encodings in a very efficient way.
I'm setting an experimental 1.5.2 installation before upgrading our whole site, and I have the following problem: while I see hebrew without problems through the whole site (without stopping to see english and spanish), I have problems in the "message" service: one computer, running on an english Windows, can write hebrew but receives cyrilic characters instead of hebrew chars; other computer, with hebrew Windows, receives hebrew without problems.
I want to emphasize that I have this problem ONLY in the Message service... (and I didn't have this problem i.e. in the dialogue module of the 1.4.3)
please, any solutions?
thanx,

daniEl