cyrus connection timeout

[Michael Hollmann]

my problem,

every day i have to restart the cyrus imap daemon.
sometimes more than once a day. still connected clients could receive
emails but new clients can't get a connection, telnet on port 143 does 
no result in "* OK server Cyrus IMAP4 v2.1.18 server ready". it seems 
master does not spawn imapd any more. after restarting the master daemon 
everything is fine.

this is the only error message in /var/log/imapd.log
- SQUAT failed to open index file

our server runs on FreeBSD 4.10-RELEASE-p18

following packages are installed:
- cyrus-imapd-2.1.18_1
- cyrus-sasl-2.1.21
- cyrus-sasl-saslauthd-2.1.19
- postfix-2.1.4,1


is this a known problem?
are there any solutions for this problem?


thanks, best regards

michael