hi

i have the same issue as you
there is a bug on something similar to this, that supposedly was fixed
[#ZF-2092] XML-RPC client fails during parsing of response with empty array on PHP-5.2.4 - Zend Framework Issue Tracker

but i've got zf 1.0.3 and php 5.2.5
and i still get that failed to parse response message, so i really don't know

just wanted to let you know, you weren't the only one

dave