Hi I believe this bug can be closed now. I posted the question on linux-kernel mailing list. A reply came back about mtu issues.
Seems like I had 2 problems net.ipv4.tcp_rmem = 4096 87380 2097152 in my sysctl.conf, a hang over from long ago and my mtu was set wrongly the route information was different from the ip li information I had ip r a 192.168.11.10/32 dev eth0 mtu 9100 ip li set eth0 mtu 6144 since clearing these up I haven't had any problems, I was able to previously reproduce the probem by coping over a 2G file Alex
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