Down load the updates. The fix for your problem might be within them. Drivers are often down loaded with the updates for your Ethernet adapter chip or card. A large percentage of these are security up dates, to keep your computer safe. You should up date your PC(s).
Then double check your Email settings. Seek information from your IP if you are uncertain about them.
Check to see if your telephone line connection are correct. Unplug them then plug them in again. (If your have a spare filter for a DSL connection then switch them. The current one for the spare.)
Disconnect all the connection from your router/modem then reconnect them after one minutes. This will reset the hardware. This includes transformers. Restart your computer.
Discontent the LAN try each PC/Laptop on the connection. Did either of them work?
Did your Ethernet adapter come with diagnostics? Run them.
Do this trouble shooter for Internet Explorer 7: