Can't get DHCP IP

Dear Experts,
I have a TI DM8148 EVM board REV C, the EZSDK5.05 SW package, and DVRRDK1.09 SW package.
EZSDK5.05, DVRRDK1.09 both use Linux2.6.37, however, there are some modifications between these two kernels.

When I use uImage of DVRRDK1.09 to boot up EVM board, this board can be given a DHCP IP from my office network, but uImage of EZSDK5.05 can't. I try to build a DHCP Server on my local PC, let EZSDK5.05 and DVRRDK1.09 get DHCP IP from my local PC, both uImage can get DHCP IP. Any body can tell me what's the problem ??

(One board with two version kernel, one kernel can get DHCP IP from my office network, the other one can't. But both kernel can get DHCP IP from my local DHCP server.)

Thx ~

oobin