Zend_Soap_Client_Common::__doRequest
should be renamed to
Zend_Soap_Client_Common::_doRequest
with php 5.2.5 that caused a seg fault, most properly due to an endless recursion.
Maybe its a php bug too, i'll check it but for sure this is a bug in Zend_Soap_Client_Common.
That took some time to find 
Regards Frank Ruske
Confirmed from me