Varnish Error 503 Service Unavailable

[Brano]

Hi all,

recently we installed Varnish on our server. Everything works fine,
but on download we get this error:

http://www.opensubtitles.org/en/download/file/1951965961

Varnish Error 503 Service Unavailable

Service Unavailable
Guru Meditation:

XID: 2138997704

My backend works ok:
http://web1.opensubtitles.org/en/download/file/1951965961
http://web2.opensubtitles.org/en/download/file/1951965961

Server info:
varnishd (varnish-2.0.1)
OS: FreeBSD 7.1-PRERELEASE
PHP Version 5.2.6
httpd: Lighttpd 1.4.20

Here is log:
  276 ReqStart     c 124.157.249.3 50073 2138997704
  276 RxRequest    c GET
  276 RxURL        c /en/download/file/1951965961
  276 RxProtocol   c HTTP/1.1
  276 RxHeader     c Host: www.opensubtitles.org
  276 RxHeader     c User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3 (.NET CLR 3.5.30729)
  276 RxHeader     c Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  276 RxHeader     c Accept-Language: en
  276 RxHeader     c Accept-Encoding: gzip,deflate
  276 RxHeader     c Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
  276 RxHeader     c Keep-Alive: 300
  276 RxHeader     c Connection: keep-alive
  276 RxHeader     c Referer: http://www.opensubtitles.org/en/subtitles/3363915/prison-break-en
  276 RxHeader     c Cookie: __utma=188827125.1293269160.1192786702.1226384704.1226387542.495; __utmz=188827125.1226166768.475.44.utmccn=(referral)|utmcsr=forum.opensubtitles.org|utmcct=/index.php|utmcmd=refe
  276 RxHeader     c Cache-Control: max-age=0
  276 VCL_call     c recv
  276 VCL_return   c lookup
  276 VCL_call     c hash
  276 VCL_return   c hash
  276 VCL_call     c miss
  276 VCL_return   c fetch
  139 BackendOpen  b web2 92.240.234.126 61634 92.240.234.119 80
  276 Backend      c 139 www_director web2
  139 TxRequest    b GET
  139 TxURL        b /en/download/file/1951965961
  139 TxProtocol   b HTTP/1.1
  139 TxHeader     b Host: www.opensubtitles.org
  139 TxHeader     b User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-GB; rv:1.9.0.3) Gecko/2008092417 Firefox/3.0.3 (.NET CLR 3.5.30729)
  139 TxHeader     b Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
  139 TxHeader     b Accept-Language: en
  139 TxHeader     b Accept-Encoding: gzip,deflate
  139 TxHeader     b Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
  139 TxHeader     b Referer: http://www.opensubtitles.org/en/subtitles/3363915/prison-break-en
  139 TxHeader     b Cookie: __utma=188827125.1293269160.1192786702.1226384704.1226387542.495; __utmz=188827125.1226166768.475.44.utmccn=(referral)|utmcsr=forum.opensubtitles.org|utmcct=/index.php|utmcmd=refe
  139 TxHeader     b X-Varnish: 2138997704
  139 TxHeader     b X-Forwarded-For: 124.157.249.3

If you need more info, please let me know.

Any help appreciated.

Thank you.

/Brano