O.K. I got called into a medical clinic to look at a computer that would not connect to the internet or any local network resources (this is a small 3 computer LAN used for a small medical clinic). I first checked the cable and verified it as working. I gave the computer in question a static ip address and it looked like it connected but still would/could not ping local address's. I removed the internet security to see if the firewall was somehow stopping anything. Nope same results. no connection.
I took the computer back to my shop as i thought it might be a faulty NIC (it's onboard) plugged it in and it connect via DHCP no problem. The only thing that could be blocking it is the router. I did go into the router and changed the ip address that was given to that computer as it was in a DHCP reservation list.
The computers were all turned off and no one was using them for 4 days as it was easter holidays. When they came back in and fired the computers up just one of them would not connect. What would cause this to happen? I'm like WTF?