[squid-users] (107) Transport endpoint is not connected

hi list!

i just installed squid 2.6.5-4 (on debian etch) and often get

The following error was encountered:
     * Read Error
The system returned:
     (107) Transport endpoint is not connected

this occures in about 30% of the the requests. /var/log/squid/access.log says:

--- /var/log/squid/access.log
1174291587.400 3683 172.16.0.31 TCP_MISS/502 1481 GET
http://www.squid-cache.org/ - DIRECT/12.160.37.9 text/html
1174291588.384 907 172.16.0.31 TCP_MISS/200 1339 GET
http://www.squid-cache.org/favicon.ico - DIRECT/12.160.37.9 image/x-icon

---
just hitting the "reload" button of the browsers, btw.: tested with  
ie7 and firefox, does lead to the correct display, sometimes reload  
has to be pressed three times, the the log file says:
--- /var/log/squid/access.log
1174291602.906    490 172.16.0.31 TCP_MISS/200 6490 GET  
http://www.squid-cache.org/ - DIRECT/12.160.37.9 text/html
1174291603.163    257 172.16.0.31 TCP_MISS/200 1871 GET  
http://www.squid-cache.org/Icons/squid-name4.gif - DIRECT/12.160.37.9  
image/gif
1174291603.449    480 172.16.0.31 TCP_MISS/200 1005 GET  
http://www.squid-cache.org/Icons/cache_now.gif - DIRECT/12.160.37.9  
image/gif
1174291603.469    468 172.16.0.31 TCP_MISS/200 2274 GET  
http://www.squid-cache.org/Icons/squidnow.gif - DIRECT/12.160.37.9  
image/gif
1174291604.172   1216 172.16.0.31 TCP_MISS/200 34058 GET  
http://www.squid-cache.org/graphics/squid-shade.png -  
DIRECT/12.160.37.9 image/png
---
the squid.conf does not contain something "special", just an acl for  
the local net:
--- /etc/squid/squid.conf
http_port 3128
hierarchy_stoplist cgi-bin ?
acl QUERY urlpath_regex cgi-bin \?
cache deny QUERY
acl apache rep_header Server ^Apache
broken_vary_encoding allow apache
access_log /var/log/squid/access.log squid
hosts_file /etc/hosts
refresh_pattern ^ftp:           1440    20%     10080
refresh_pattern ^gopher:        1440    0%      1440
refresh_pattern .               0       20%     4320
acl all src 0.0.0.0/0.0.0.0
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255
acl to_localhost dst 127.0.0.0/8
acl purge method PURGE
acl CONNECT method CONNECT
acl hawalius src 172.16.0.0/16
http_access allow manager localhost
http_access deny manager
http_access allow purge localhost
http_access deny purge
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localhost
http_access allow hawalius
http_access deny all
http_reply_access allow all
icp_access allow all
cache_effective_group proxy
coredump_dir /var/spool/squid
---
bypassing the proxy (no proxy entry in the browser) does never lead to  
unproper display or network errors so squid seems to produce the  
errors and it is not a network problem.
What does "Transport endpoint is not connected" mean and how can i solve this?
Thanks in advance for any hints!
regards
   markus
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