IDLE: error sending message

[Giuseppe Ravasio (LU)]

Hi,
I've just migrated a quite busy cyrus install to 2.5.7.
It seems all going well except for the fact that in the logs there are a
lot of messages like:

Feb  8 09:07:06 mail cyrus/imaps[13868]: IDLE: error sending message
DONE to idled for mailbox ${SHARED_FOLDER}: Resource temporarily
unavailable.

and
Feb  8 09:14:27 thot cyrus/imaps[10661]: IDLE: error sending message
INIT to idled for mailbox ${SHARED_FOLDER}: Resource temporarily
unavailable. Falling back to polling every 60 seconds.


All the log messages refers to two folders that are shared to and
subscribed by all users.

I couldn't find any hint about this error with google.

I hope that someone could explain me this message.

Thanks
Giuseppe