lmtp timed out while sending MAIL FROM

[Gerard]

I am having a very strange issue where the imap server stops accepting
messages via LMTP, does not allow logins via imap, and the load
reaches anywhere from 800 - 2000. This happens nearly daily. Also, I
notice there are generally many defunct processes and the below pasted
excerpt from the maillog

Nov 25 06:27:11 imap06 postfix/lmtp[16300]: 22E2E10B00C3:
to=<user at domain.com>,
relay=/var/imap/socket/lmtp[/var/imap/socket/lmtp],
delay=300, status=deferred (conversation with
/var/imap/socket/lmtp[/var/imap/socket/lmtp] timed out while sending
MAIL FROM)

We are running RHEL4U4 with the version of Cyrus that comes with it
cyrus-imapd-2.2.12-3.RHEL4.1. Anyone seen something similar or have an
idea what could be causing this issue?