From: Mike N 

>    That would disable Window Scaling.   Linux uses Window scaling > 1,
> whereas Windows uses a scale = 1.   Scaling is used to send packets
> back-to-back.   As soon as the server needs to send back-to-back
> packets, it looks at the Linux Window size, and if has not scaled it,
> the server will think it has filled the Linux RX buffer and may also
> drop the MTU to match.

   Also, Geo - could it be your router?

  http://lwn.net/Articles/92727/

   I checked my router and it is passing the window Scaling field OK.

   [At first I thought it was my router - it's a dumb Linksys that
rewrites the TTL field on SYN packets to 255]

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