|In the case of a computer with both a wired NIC and a wireless NIC, and you're trying to connect via the wired NIC, disable the wireless NIC and see if the wired one doesn't start working properly.|
Open a command prompt window (Start >> Run >> type cmd and hit Enter) on the box that is working and one, or all, of the ones that aren't working if the above doesn't fix the issue. Perform the following command on them:
Post the output (labelled according to the PC it came from) in a response so we can have a look. For info on how to copy/paste from a command prompt window, click on my name above in my response and read my "how-to" guide titled, "Post the output of ipconfig (version 2)"
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.