[Dovecot] Lots of assertion PANICs in error log

[Yates Ian Mr (ITCS)]

I have just upgraded to dovecot 1.1.2 and am seeing lots of the
following panic messages filling up the error logs:

dovecot: Aug 29 09:34:32 Panic: IMAP(user): file index-sync.c: line 39
(index_mailbox_set_recent_uid): assertion failed:
(seq_range_exists(&ibox->recent_flags, uid))
dovecot: Aug 29 09:34:32 Error: IMAP(user): Raw backtrace: imap
[0x483888] -> imap [0x484293] -> imap [0x483a46] ->
imap(index_mailbox_set_recent_seq+0) [0x453f80] ->
imap(index_mailbox_set_recent_seq+0x43) [0x453fc3] -> imap [0x43b3e8] ->
imap(mbox_sync+0x380) [0x43bdd0] -> imap [0x434bcd] ->
imap(index_transaction_commit+0x3c) [0x454f3c] -> imap(cmd_copy+0x344)
[0x4167d4] -> imap(cmd_uid+0x52) [0x41a6c2] -> imap [0x41b723] -> imap
[0x41b6e8] -> imap [0x41b9ba] -> imap(client_input+0x63) [0x41bb93] ->
imap(io_loop_handler_run+0x109) [0x48b029] -> imap(io_loop_run+0x28)
[0x48a3f8] -> imap(main+0x3f2) [0x423272] ->
/lib64/tls/libc.so.6(__libc_start_main+0xdb) [0x337911c40b] -> imap
[0x41578a]
dovecot: Aug 29 09:34:32 Error: child 25658 (imap) killed with signal 6

This is just the latest example from this morning, there are plenty to
choose from!

My system setup is a RHEL4.6 64bit install.

I have tried clearing out the old cache files (dovecot.index,
dovecot.cache etc) for all the users but I'm still seeing these crash
dumps filling my logs. 

Help!

If you require any further information please let me know.

I.