[squid-users] error "Detected Dead Parent" in cache

Hi, any idea what could be causing “Detected
DEAD Parent: proxy1.test.au/3128 failed”

2012/03/20 11:29:38| helperOpenServers:
Starting 10 'squid_ldap_auth' processes

2012/03/20 11:29:38| helperOpenServers:
Starting 5 'squid_ldap_group' processes

2012/03/20 11:29:38| Accepting proxy HTTP
connections at 0.0.0.0, port 3128, FD 26.

2012/03/20 11:29:38| Accepting ICP messages
at 0.0.0.0, port 3130, FD 27.

2012/03/20 11:29:38| WCCP Disabled.

2012/03/20 11:29:38| Configuring Parent proxy1.test.au/3128/3130

2012/03/20 11:29:38| Configuring Parent proxy2.test.au
/3128/3130

2012/03/20 11:29:38| Configuring Parent proxy3.test.au
/3128/3130

2012/03/20 11:29:38| Configuring Parent proxy4test.au
/3128/3130

2012/03/20 11:29:38| Loaded Icons.

2012/03/20 11:29:38| Ready to serve
requests.

2012/03/20 11:29:40| TCP connection to proxy1.test.au
/3128 failed

2012/03/20 11:29:43| TCP connection to  proxy1.test.au /3128 failed

2012/03/20 11:29:45| TCP connection to  proxy1.test.au /3128 failed

2012/03/20 11:29:46| TCP connection to proxy1.test.au
/3128 failed

2012/03/20 11:29:56| Detected DEAD Parent: proxy1.test.au

2012/03/20 11:29:57| TCP connection to
proxy1.test.au/3128 failed

2012/03/20 11:30:00| TCP connection to
proxy1.test.au/3128 failed

2012/03/20 11:30:01| Detected DEAD Parent:
proxy3.test.au

2012/03/20 11:30:01| Detected DEAD Parent:
proxy4.test.au

2012/03/20 11:30:01| Detected DEAD Parent:
proxy2.test.au

2012/03/20 11:30:14| TCP connection to
proxy1.test.au/3128 failed
Received on Tue Mar 20 2012 - 03:25:48 MDT