[Dovecot] messages downloading repeatedly to mozilla/seamonkey pop3 client

[Ben Julian]

Hello Dovecot List,
  I am a bit of a sysadmin novice and this is my first time emailing,
so please let me know if I have left some critical information out.  I
am supporting a small office network supported primarily by linux
servers.  All of my users are using dovecot as a pop3 daemon on a
centOS 5 box, no IMAP users.  Seven users are running outlook 2003 on
windows XP, two users are running thunderbird on ubuntu, two are
running evolution on ubuntu, and one is running mozilla seamonkey on
XP.  Emails to the mozilla/seamonkey user are downloading multiple
times, but not to any of the other users.

A typical maillog report following this user's mail client pop3 login:

Mar  3 10:37:00 servername dovecot: pop3-login: Login: user=<user>,
method=PLAIN, rip=::ffff:192.168.99.13, lip=::ffff:192.168.99.4
Mar  3 10:37:00 servername dovecot: POP3(user): mbox sync: UID
inserted in the middle of mailbox /var/mail/user (84873 > 84872,
seq=2, idx_msgs=3)
Mar  3 10:37:01 servername dovecot: POP3(user): mbox sync: UID
inserted in the middle of mailbox /var/mail/user (84877 > 84872,
seq=2, idx_msgs=4)
Mar  3 10:37:01 servername dovecot: POP3(user): Disconnected: Logged
out top=0/0, retr=1/3364, del=1/1, size=3347

Things I've tried:
*adding the following lines to dovecot.conf:
protocol pop3 {
  pop3_uidl_format = %08Xu%08Xv
  pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
}
*deleting the user's homedir mail directory (including all dovecot index files)
*restarting dovecot
*changing mail clients: tried outlook express, netscape 4.8,
thunderbird on user's PC
*restarting the server

All changes resulted in only a brief (1-2hr) cessation of the problem.

I've subscribed for a month or so now and searched the archives, but
if I missed a solution to this in there, I apologize.
Thanks,
Ben Julian