Localisation problem : lost my translation

I am running WordPress for a few months with a french localisation file (fr_FR.mo). But for a few days, the site is completely in English.

I can’t find where the problem comes from…

• The mo file is readable and in the good location (/wp-includes/languages/fr_FR.mo)
• The WPLANG constant is well defined
• The default domain is loaded

But the problem is that WordPress does’nt recognize the mo file as a real mo file. In the gettext_reader class I get an error code 1. It seems like the Byte Order detection failed…

Note : I upgraded to 1.5.2 and the problem is still unsolved.

Note 2 : My host moved recently my account to a new server. I think the problem came with that new server but I can’t find what is the problem on the server…

Tahnks for your ideas…