Moving/renaming IMAP folders

I’m trying to rename some IMAP folders, but Dovecot’s refusing to play ball with an error "Renaming not supported across conflicting directory permissions". This is what I get (this comes from Roundcube in IMAP debug mode);

Code:

[27-Oct-2012 15:15:43 +0000]: [0A8E] S: * OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE STARTTLS AUTH=PLAIN] Dovecot DA ready.
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0001 ID ("name" "Roundcube Webmail" "version" "0.8.2" "php" "5.3.18" "os" "Linux" "command" "/roundcube/?_task=settings&_action=rename-folder")
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: * ID NIL
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0001 OK ID completed.
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0002 AUTHENTICATE PLAIN <auth string>
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0002 OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE IDLE SORT SORT=DISPLAY THREAD=REFERENCES THREAD=REFS THREAD=ORDEREDSUBJECT MULTIAPPEND UNSELECT CHILDREN NAMESPACE UIDPLUS LIST-EXTENDED I18NLEVEL=1 CONDSTORE QRESYNC ESEARCH ESORT SEARCHRES WITHIN CONTEXT=SEARCH LIST-STATUS SPECIAL-USE] Logged in
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0003 LIST (SUBSCRIBED) "" "Development.GAL002.*"
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0003 OK List completed.
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0004 LSUB "" Development.GAL002
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: * LSUB () "." "Development.GAL002"
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0004 OK Lsub completed.
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0005 RENAME Development.GAL002 Archive.GAL002
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0005 NO [CANNOT] Renaming not supported across conflicting directory permissions
[27-Oct-2012 15:15:43 +0000]: [0A8E] C: A0006 LOGOUT
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: * BYE Logging out
[27-Oct-2012 15:15:43 +0000]: [0A8E] S: A0006 OK Logout completed.


Using default DirectAdmin install/configs all around, nothing unusual in the setup. Thunderbird also reports the same error when I try and move one folder to another. Dovecot is running version 2.1.10.

Any ideas?

Dan