It means the OSD wasn't able to successfully fetch the kernel from the
TFTP server. Check that your PC actually has the IP 192.168.1.200, and
that it is configured to allow the OSD's IP 192.168.1.100 to access
it. Next check that the path "/images/uImage/" is correct.
More information (if you haven't found it already) is at:
http://wiki.neurostechnology.com/index.php/OSD_2.0_Development#Net-booting_your_device
Hope this helps,
Matthew