I have set up a transparent proxy bridge with squid and dansguardian, only everything seems to work perfectly but for downloads.
I can't seem to download anything.
The download starts, then after a while I see that it cuts.Small files are able to download.Bigger files (larger than 5MB), cuts with a message "connection with the server was reset" !

My configuration is as follows :

ifconfig eth0 promisc up
ifconfig eth1 promisc up

brctl addbr br0
brctl addif br0 eth0
brctl addif br0 eth1

ifconfig br0 xxx.xxx.xxx.xxx netmask up
route add default gw yyy.yyy.yyy.yyy dev br0

Rules for the firewall:

ebtables -t broute -A BROUTING -p IPv4 ip-protocol 6 ip-destination-port 80 -j redirect redirect-target ACCEPT
iptables -t nat -A PREROUTING -i eth0 -p tcp dport 80 -j REDIRECT to-port 8080
iptables -t nat -A PREROUTING -i eth1 -p tcp dport 80 -j REDIRECT to-port 8080
iptables -t nat -A PREROUTING -i br0 -p tcp dport 80 -j REDIRECT to-port 8080

where port 8080 is the dansguardian port.

Internet Browsing looks fine and quick, only the problem is with the downloads.
Any idea of what is happening, and why does the connection resets and the downloads cut ?
I have 500 users connected to this transparent bridge,
any help is much appreciated.