Problem with Mail_Mime (RFC822::parseAddressList)

I am having a problem with Mail_Mime version 1.2.1, in conjunction with Horde/IMP. I periodically get the following error in my php error log: PHP Fatal error: Call to undefined function: raiseerror() in /usr/local/depot/php-4.3.2/lib/php/Mail/RFC822.php on line 189 I compared RFC822.php in Mail_Mime 1.2.1 to the version in 1.0.2 (which I was previously running), and see that Mail/RFC822.php no longer appears to extend the PEAR base class, which is where raiseError() seems to be defined. Is this a configuration error on my part, or a problem with Mail_Mime? Any help would be appreciated. I'm running PHP 4.3.2, with the following PEAR modules installed: Installed packages: =================== Package Version State Archive_Tar 1.1 stable Console_Getopt 1.0 stable DB 1.5.0RC1 stable Date 1.3.1beta beta HTTP 1.2.1 stable Log 1.7.0 stable Mail 1.1.1 stable Mail_Mime 1.2.1 stable Net_SMTP 1.2.3 stable Net_Sieve 0.8.1 stable Net_Socket 1.0.1 stable PEAR 1.2.1 stable XML_Parser 1.0.1 stable XML_RPC 1.0.4 stable -- Gary Windham Systems Programmer, Principal The University of Arizona, CCIT