"status=deferred (delivery temporarily suspended"

I have an Intel Xserve running 10.4.10

Some months ago I upgraded clamav, amavisd-new, spamassassin and squirrel mail using the articles from Alex at http://osx.topicdesk.com/content/category/4/18/62/
(Thanks Alex)
All has been working well.

On Friday night my mail stopped delivering mail to internal recipients with the following in the logs:
status=deferred (delivery temporarily suspended)

All mail was sitting in the queue

I tried a restart on amavisd, but a reboot of the system got it going and retrying all the mail in queue finally dribbled out to end users.

I have come in this morning with the same scenario

Feb 12 08:48:37 fileserver postfix/qmgr[28609]: 0A80620B6E96: to=<info@company.co.uk>, relay=none, delay=-3867, status=deferred (delivery temporarily suspended: connect to 127.0.0.1[127.0.0.1]: Connection refused)

I was getting moaned at so have done a reboot, which again has cured the issue.

If anyone can give any pointers as what to look for, or what I can do to stop it occurring, logs appear to show that one minute a mail was being handled correctly, the next it isn't.
I have posted machine info below

spamassassin -V
SpamAssassin version 3.2.3
running on Perl version 5.8.6
amavisd -V
amavisd-new-2.5.2 (20070627)
clamscan -V
ClamAV 0.91.1/5779/Mon Feb 11 19:56:48 2008

postconf -n
command_directory = /usr/sbin
config_directory = /etc/postfix
content_filter = smtp-amavis:[127.0.0.1]:10024
daemon_directory = /usr/libexec/postfix
debug peerlevel = 2
disable vrfycommand = yes
enable serveroptions = yes
html_directory = no
inet_interfaces = all
local recipientmaps = proxy:unix:passwd.byname $alias_maps
luser_relay =
mail_owner = postfix
mailbox sizelimit = 0
mailbox_transport = cyrus
mailq_path = /usr/bin/mailq
manpage_directory = /usr/share/man
maps rbldomains =
message sizelimit = 0
mydestination = $myhostname, localhost.$mydomain, fileserver.company.co.uk, company.co.uk,company.com, company4.co.uk,company4.com, reportwell.co.uk,reportwell.com, company3solutions.co.uk,company3solutions.com company2solutions.co.uk, company2solutions.com
mydomain = company.co.uk
mydomain_fallback = localhost
myhostname = mail.company.co.uk
mynetworks = 127.0.0.1/32,10.1.0.0/16,10.10.1.0/24,192.168.99.0/24,10.12.1.118/32
mynetworks_style = host
newaliases_path = /usr/bin/newaliases
queue_directory = /private/var/spool/postfix
readme_directory = /usr/share/doc/postfix
relayhost =
sample_directory = /usr/share/doc/postfix/examples
sendmail_path = /usr/sbin/sendmail
setgid_group = postdrop
smtpd clientrestrictions = permit saslauthenticated, permit_mynetworks, reject rblclient zen.spamhaus.org, reject rblclient bl.spamcop.net, permit
smtpd datarestrictions = permit_mynetworks, reject unauthpipelining, permit
smtpd helorequired = yes
smtpd helorestrictions = permit saslauthenticated, permit_mynetworks, check heloaccess hash:/etc/postfix/helo_access, reject non_fqdnhostname, reject invalidhostname, permit
smtpd pw_server_securityoptions = plain
smtpd recipientrestrictions = reject invalidhostname, reject non_fqdnsender, reject non_fqdnrecipient, permit saslauthenticated, permit_mynetworks, hash:/etc/postfix/protected_destinations, reject unauthdestination, reject unlistedrecipient, hash:/etc/postfix/access, reject rblclient zen.spamhaus.org, reject rblclient bl.spamcop.net, permit
smtpd sasl_authenable = yes
smtpd senderrestrictions = permit saslauthenticated, permit_mynetworks, reject non_fqdnsender, permit
smtpd tls_keyfile =
smtpd use_pwserver = yes
unknown local_recipient_rejectcode = 550


I am also not getting my confirmation mails from sa-learn each evening at all.