[Dovecot] error in 1.1.2

[Cor Bosman]

Ive been getting a LOT of these errors since 1.1.2: So far ive seen this
with 1800 customers, and we're getting active complaints about errors in
imap clients.  When I check the users log I always see this error..
This always happens with COPY commands in Squirrelmail. 

Sep  2 20:09:35 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): rename(/var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache.lock, /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache) failed: No such file or directory
Sep  2 20:09:35 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): rename(/var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache.lock, /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache) failed: No such file or directory
Sep  2 20:09:35 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): file_dotlock_replace() failed with index cache file /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache: No such file or directory
Sep  2 20:09:35 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): file_dotlock_replace() failed with index cache file /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache: No such file or directory
Sep  1 20:14:06 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): rename(/var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache.lock, /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache) failed: No such file or directory
Sep  1 20:14:06 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): rename(/var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache.lock, /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache) failed: No such file or directory
Sep  1 20:14:06 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): file_dotlock_replace() failed with index cache file /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache: No such file or directory
Sep  1 20:14:06 userimap4.xs4all.nl dovecot: IMAP(xxxxxxx): file_dotlock_replace() failed with index cache file /var/spool/mail/dovecot-control/indexes/j/jd/xxxxxxx/.Inveztor/dovecot.index.cache: No such file or directory

FreeBSD 6.2, NFS storage for everything. Any idea?

Cor