The problem can be corrected by upgrading the affected package to version 4:4.3.8-3ubuntu7.10 (for Ubuntu 4.10), or 4:4.3.10-10ubuntu3.2 (for Ubuntu 5.04). In general, a standard system upgrade is sufficient to effect the necessary changes.
USN-147-1  fixed a remote code execution vulnerability in the XMLRPC module of the PEAR library. Unfortunately the packages announced in USN-147-1 were faulty and shipped broken xmlrpc modules. The updated packages ship correct modules.