The imap rpm that comes with RH5.9 does not include the pam config file for the ipop3d. This causes ipop3d to just sit, hang and eventually disconnect when a user tries to connect to the server. The imap rpm is severely lacking documentation so it took a strace to determine the problem. The fix is to copy /etc/pam.d/imap to /etc/pam.d/pop .
This has been fixed.