I did mention in the class description that this class depends on PEAR::POP3 and PEAR::Mail_MIME, both of which can be installed by using the pear installer. As root go: pear install Net_POP3 and then pear install Mail_MIME and everything should work OK. If you don't have pear installed, then go to http://pear.php.net and follow the instructions there for your platform.
Any other problems, please post here! This is a good class, and I would like to see you succeed with it!