too long

I have a PHP xmlrpc-client (http://phpxmlrpc.sourceforge.net/) calling a remote PHP xmlrpc-server. Most of the time it works but sometimes it fails with,

Invalid return payload: enable debugging to examine incoming payload (XML error at line 1, check URL).

On enabling debug, I got the error info as,

<PRE>---GOT---

HTTP/1.1 200 OK

Date: Wed, 07 Dec 2011 03:39:02 GMT

Server: Apache/2.2.16 (Ubuntu)

X-Powered-By: PHP/5.3.3-1ubuntu9.3

Vary: Accept-Encoding

Content-Encoding: gzip

Content-Length: 266

Connection: close

Content-Type: text/html

.

.

cannot serialize xmlrpcresp objects whose content is native php values.

The content type is shown as html instead of xml, is this the issue ?. I would like to get some help to proceed further.