imapd signaled to death when server-side sorting on Subject

[Michael Sims]

Hi,

I'm seeing something funny here I was hoping that someone could help me with.  I had
a user complain that when he sorts his mail by Subject in our webmail interface
(Horde/IMP), all of his messages disappear.  I investigated and discovered the
problem is occuring when IMP attempts to get a list of UIDs from the server sorted
by Subject.  The telemetry log for this user shows that the command issued is like
so:

. UID SORT (SUBJECT) US-ASCII ALL

At this point imapd closes the connection.  This problem does not happen when
sorting on any other field, and it thus far seems to be only happening with this
user's mailbox (although I have heard similar reports in the past and was never able
to reproduce this before).

At maximum verbosity, syslog's log file shows that the imapd process was "signaled
to death by 7":

Aug 17 11:04:32 mail imapd[1050]: login: localhost.localdomain[127.0.0.1] ****
plaintext
Aug 17 11:04:32 mail imapd[1050]: seen_db: user **** opened
/var/imap/user/j/****.seen
Aug 17 11:04:33 mail imapd[1050]: open: user **** opened INBOX
Aug 17 11:04:33 mail master[904]: process 1050 exited, signaled to death by 7

My server's vitals:

Cyrus IMAP v2.1.18 (I know, I need to upgrade to 2.2.x, haven't had a chance yet)
Linux (Red Hat EL 2.1, Kernel 2.4.9-e.27smp)

Has anyone seen something similar, or would anyone have any idea where I could start
looking?  I tried running a reconstruct on this user's mailbox, but that didn't have
any affect.  I'd greatly appreciate any help...