[U-Boot] uboot not responding to ping to ubuntu

[Embedded User]

Hi All,

I am facing a very strange problem. I have a MINI2440 SBC which I am
connecting to my laptop with Ubuntu11.04. I have downloaded the Uboot
configured for mini2440 and its version is 1.3.2. I have successfully
transferred the Uboot code on the SBC. But when I am trying to do a TFTP
from the SBC to my laptop its failing.
I have enabled debug prints in Uboot and am monitoring packets received on
Wireshark on my laptop. I see that uboot sends ARP requests and the Host
replies back, but these are not acknowledged by the Uboot on SBC. Eventually
it timeouts. Ping also fails.
Then I connected my SBC to windows Xp based Host machine and in this case
when Uboot sent out ARP requests these were received and acknowledged by
Uboot and accordingly a ping was successful.
My ubuntu based laptop was also able to ping to my windows machine and
viceversa.
The wireshark dumps for ARP replies from both Ubuntu and Windows to the
Uboot looked the same with the source MAC address being different.
So I am missing some configuration on my Ubuntu11.04 or what else could be
the problem.

Thanks & Regards.