courier-imapd error: Keyword hashtable memory corruption

Dear Courier-Users list,

I have been using courier-imapd for a few years now and I must say that
I am very satisfied with the IMAP/POP3 server. Before that, I have used
imapd-uw (University of Washington) and courier has definitely been a
big improvement.

A couple of days ago, I have noted a log message in my system's maillog
file on which I would like your opinion:

------ 8< -------- 8< ---------------
Jun 18 17:59:18 <host_name> imapd-ssl: <account_name>: INTERNAL ERROR:
Keyword hashtable memory corruption.
------ 8< -------- 8< ---------------

I am not sure what to make of this and a web search did not reveal any
insights as to the cause and/or possible consequences of the reported
error. From what I can tell, there have been three (3) occurences of
this log message on different days and times. However, all messages
relate to the same user account.

My system is a (uname -a)

Linux <host_name> 3.1.6-gentoo-rinux3 #1 SMP Sat Dec 31 17:21:12 CET
2011 x86_64 Quad-Core AMD Opteron(tm) Processor 1381 AuthenticAMD GNU/Linux

The Gentoo box reports for courier and related packages:
[IP-] [  ] net-libs/courier-authlib-0.63.0-r1:0
[IP-] [  ] net-mail/courier-imap-4.5.0:0
[IP-] [  ] dev-libs/cyrus-sasl-2.1.23-r6:2