[Dovecot] Broken Debian package

[Thing]

Hi,

I have run Dovecot via Debian for some years but in the last few weeks
something has broken....I have been upgrading Debian but today rebooted it
to try and sort out a failed DLT....now I find dovecot is non-functional....

So,

Where to look for faults please? ie logs? can I make dovecot verbose?
Thunderbird if telling me Dovecot is not imap4 compliant........and I cannot
connect to it...

I have tried re-installing Dovecot but the Debian package contains no
dovecot.conf....so I have dovecot imap-d and dovecot common installed but no
config.

So I copied back the config files from a safe location....

When I start up I get,
hermes:/var/log# tail dovecot
dovecot: 2008-04-06 11:32:32 Info: Dovecot v1.0.rc15 starting up
hermes:/var/log#

So trying to connect, tail -f (on /var/log/dovecot),

dovecot: 2008-04-06 11:57:34 Info: imap-login: Login: user=<thing>,
method=plain, rip=192.168.1.101, lip=192.168.1.254, TLS
dovecot: 2008-04-06 11:57:34 Error: IMAP(thing): seq = 186, rec->uid = 0,
first_new_seq = 188, records = 187
dovecot: 2008-04-06 11:57:34 Error: child 20048 (imap) killed with signal 6
dovecot: 2008-04-06 11:57:34 Info: imap-login: Login: user=<thing>,
method=plain, rip=192.168.1.101, lip=192.168.1.254, TLS
dovecot: 2008-04-06 11:57:34 Error: IMAP(thing): seq = 186, rec->uid = 0,
first_new_seq = 188, records = 187
dovecot: 2008-04-06 11:57:34 Error: child 20050 (imap) killed with signal 6
dovecot: 2008-04-06 11:57:34 Info: imap-login: Login: user=<thing>,
method=plain, rip=192.168.1.101, lip=192.168.1.254, TLS
dovecot: 2008-04-06 11:57:34 Error: IMAP(thing): seq = 186, rec->uid = 0,
first_new_seq = 188, records = 187
dovecot: 2008-04-06 11:57:34 Error: child 20052 (imap) killed with signal 6
dovecot: 2008-04-06 11:57:35 Info: imap-login: Login: user=<phoebe>,
method=PLAIN, rip=192.168.1.102, lip=192.168.1.254, TLS
dovecot: 2008-04-06 11:57:35 Info: imap-login: Login: user=<thing>,
method=plain, rip=192.168.1.101, lip=192.168.1.254, TLS
dovecot: 2008-04-06 11:57:35 Error: IMAP(thing): seq = 186, rec->uid = 0,
first_new_seq = 188, records = 187
dovecot: 2008-04-06 11:57:35 Error: child 20062 (imap) killed with signal 6

squirrelmail is also now dead....

Ideas please?

regards

Steven