Ethernet Problem

Hi,

I'm trying to enable my development board to communicate with a PC via Ethernet. I am able to establish a connection and send data from the PC to the micro without any issues. When I try to send data from the micro to the PC, however, the PC doesn't respond to the data. WireShark, which is a network analyzer program, sees the packet, though. I have tried both TCP and UDP with the same results. Has anyone come across the same issue? I'm using NXP's LPC1758 Cortex-M3.

Thanks,
Paul