XMLRPC ISSUE PHP 5.2.5 WP 3.1.3

Hello,
I’am testing the xmlrpc functionaliaty of wordpress wich seems really nice for my needs.
It works on my local computer but does not on my server.
My computer is using the php 5.2.10 version
VS
My server is using the php 5.2.5 version
I’m testing with WordPress 3.1.3.

I precise that I could nor upgrade my phpversion nor upgrade my wordpress version because of compatibilty issues.

Does anyone knows if this problem is related to a php/wordrpress version issue or anything else ?

Thanks,
greetings
Ben