[squid-users] Fwd: What's means ? ERR_PRECONDITION_FAILED

Anyone know what is error : ERR_PRECONDITION_FAILED

This occure randomly on some request. Sometimes
on swf, sometimes on css files...

Bellow the requests and response headers..

Squid Version:
Squid Cache: Version 3.2.0.3

Best regards,

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Request URL:
http://www.bradesco.com.br/html/img/tv/filme0.swf
Request Method: GET
Status Code: 412 Precondition Failed
Request Headers
Accept: */*
Accept-Charset:
ISO-8859-1,utf-8;q=0.7,*;q=0.3
Accept-Encoding: gzip,deflate,sdch
Accept-Language: pt-BR,en-US;q=0.8,en;q=0.6
Connection: keep-alive
Cookie: CKIDP=YWO4CLCF4aOjYyoPncP9Y5p+WNFY1292850798;
CTLNC=dzvo+cmywMdZd/sc3mKtTBhtxpNY05
Host: www.bradesco.com.br
If-Modified-Since: Thu, 16 Dec 2010 17:22:02 GMT
If-None-Match: "7396-4bab-4abca280"
Referer: http://www.bradesco.com.br/html/swf/destaque.swf
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US) AppleWebKit/534.10
(KHTML, like Gecko) Chrome/8.0.552.215 Safari/534.10
Response Headers
Age:1292873418
Connection:keep-alive
Content-Language: pt-br
Content-Length: 2678
Content-Type: text/html
Date: Mon, 20 Dec 2010 19:30:17 GMT
Mime-Version: 1.0
Server: squid
Vary: Accept-Language
Via: 1.1 cache1.unetvale.com.br (squid)
Warning: 113 cache1.unetvale.com.br (squid) This cache hit is still
fresh and more than 1 day old
X-Cache: HIT from cache1.unetvale.com.br
X-Squid-Error: ERR_PRECONDITION_FAILED 0
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Alex Montoanelli
Analista de Sistemas
Unetvale Conectividade
+55 48 3263 8700
www.unetvale.net