Has this connection ever worked in the past? If so, then something you changed since then may be the cause. Try un-doing any changes you made since the connection last worked.
If that doesn't help, then try connecting another known-good system via the same wired connection. If that works, it verifies that the problem is in the system and not the wired connection (cable, switch, router, etc.). If another known-good system cannot connect via the same wired connection, then something in the connection is causing the problem.
If the problem is in the connection, then try resetting all of the components involved (switch, router, modem, etc.). If that doesn't help, then try replacing the cable with a known-good spare. Also try using a different port on the wired switch and/or router. If that doesn't help, then try replacing the switch, router, modem, etc. with known-good spares.
If the problem is in the system, then what happens when you replace the network card with a known-good spare? If that works, it verifies that the original card, driver or configuration are the problem. In that case you could try uninstalling and reinstalling the latest drivers for the card, and try resetting the Winsock protocol using the directions in the following article: How to troubleshoot network connectivity problems in Internet Explorer
Let me know what the problem/solution turns out to be. Scott.