Problema com o Squid. ERROR the requested URL could not be retrieved.

Ola pessoal;
Estou com um problema no squid que esta me tirando do serio. Tenho um server FreeBSD 5.4 rodando squid e ja a algum tempo esta ocorrende de algumas paginas nao esta abrindo e surge a seguinte msg de erro: ERROR the requested URL could not be retrieved. Quando eu desabilito o squid o problema desaparece. vou postar meu squid.conf e minhas regras do ipfw. Desde ja agradeço a ajuda de todos e aguardo logo poder acabar com esse problema. Grato.

##
## Configuracoes de rede
##
############################################
http_port 192.168.0.1:3128
##http_port 127.0.0.1:3128

##
## Configuracoes de memoria e cache
##
############################################
cache_mem 64 MB
cache_swap_low 90
cache_swap_high 95
maximum_object_size 4096 KB
minimum_object_size 0 KB
maximum_object_size_in_memory 32 KB
ipcache_size 1024
ipcache_low 90
ipcache_high 95
fqdncache_size 512
cache_replacement_policy lru

##
## Definicao dos arquivos e log
##
############################################
cache_dir ufs /usr/squid/cache 150000 16 256
cache_access_log /usr/squid/log/access.log
cache_log /usr/squid/log/cache.log
cache_store_log /usr/squid/log/store.log
cache_store_log none

emulate_httpd_log off
log_ip_on_direct on
mime_table /usr/local/etc/squid/mime.conf
log_mime_hdrs off
pid_filename /usr/squid/run/squid.pid
debug_options ALL,1
log_fqdn off
client_netmask 255.255.255.255
ftp_user [email protected]
ftp_list_width 32
ftp_passive on
ftp_sanitycheck on
ftp_telnet_protocol on

# diskd_program /usr/lib/squid/diskd
# unlinkd_program /usr/lib/squid/unlinkd

auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours

request_header_max_size 10 KB
request_body_max_size 0 KB

##
## Padrao de atualizacao do cache.
##
#########################################################################

refresh_pattern ^ftp: 1440 20% 10080
refresh_pattern ^gopher: 1440 0% 1440
refresh_pattern . 0 20% 4320

##
## Listas de controle de acesso - ACLs
##
############################################

acl QUERY urlpath_regex cgi-bin \?
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255

acl conecta src 192.168.0.0/255.255.0.0
acl GOVERNO dstdomain .gov.br

acl ALL src 0.0.0.0/0.0.0.0
acl to_localhost dst 127.0.0.0/8

acl SSL_ports port 443 563
acl Safe_ports port 80 # http
acl Safe_ports port 21 # ftp
acl Safe_ports port 443 563 # https, snews
acl Safe_ports port 70 # gopher
acl Safe_ports port 210 # wais
acl Safe_ports port 1025-65535 # unregistered ports
acl Safe_ports port 280 # http-mgmt
acl Safe_ports port 488 # gss-http
acl Safe_ports port 591 # filemaker
acl Safe_ports port 777 # multiling http
acl CONNECT method CONNECT

no_cache deny QUERY

http_access allow conecta
http_access deny manager
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access deny to_localhost
http_access allow ALL
http_access deny ALL
http_reply_access allow all
icp_access deny all
http_reply_access allow all
icp_access deny all
reply_body_max_size 0 allow all
cache_mgr admincache

visible_hostname servidor1.serv.com.br

cache_effective_user squid
cache_effective_group squid

logfile_rotate 0
tcp_recv_bufsize 0 bytes

httpd_accel_port 80
httpd_accel_host virtual
httpd_accel_uses_host_header on
httpd_accel_with_proxy on

#========FIM DO SQUID.CONF===========

#=========REGRAS DO IPFW=============

natd -s -p 8668 -n vr0
ipfw add 9 allow tcp from me to any
ipfw add 10 fwd 127.0.0.1,3128 tcp from any to any 80
ipfw add 11 allow ip from any to any via lo0
ipfw add 12 deny ip from any to 127.0.0.0/8
ipfw add 13 divert 8668 all from any to any via vr0
ipfw add 14 deny udp from any to any 137
ipfw add 15 deny udp from any to any 138
ipfw add 16 deny udp from any to any 139

#=========FIM DO IPFW================

Complementando esse server tem hd de 80 gb e 1 gb de ram.