Jason,

This may sound like snake oil, but I was having similar duplex problems as well as many other ethernet issues.  I found this post:

http://www.nabble.com/Re%3A-Networking-Problems-Cropping-Up-w--NetWiFiuSD-p18660920.html

and did what it suggested: put some paper between the gumstix boards to keep them from touching.  Voila!  All my ethernet problems went away, as well as many other intermittent gumstix problems

I have veredex/netwifimicroSD in this situation

-robert

On Mon, Sep 22, 2008 at 3:25 AM, <gumstix-users-request@lists.sourceforge.net> wrote:

From: Jason P Winters <jason@txt.com>
Subject: [Gumstix-users] Auto negotiation not supported?
To: gumstix-users@lists.sourceforge.net
Message-ID: <48D6FC2D.5020608@txt.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hey all..

    Well, I finally got a good build, and flashed my gumstix.  I hooked
up the serial port and a net-cf to it, and booted.   During boot, I saw
the message "Eth0 up: 100mbit full duplex" and I thought everything was
good.

  Then it got almost to the login prompt, and started spitting out
"auto negotiation NOT supported" and the NETDEV WATCHDOG: eth0: transmit
timed out" messages again.

Any clues what is going on?  This is a straight basic connex build..

Thanks in advance..

Jason