We had a problem at work the other day which took some working out to actually figure out what was wrong.
Some of the computers had gone down for no apparent reason. They lacked access to the server and to the internet, yet others had access. I thought that it might be the firewall license, or a virus, or something wrong with the server itself.
Anyway the 24 port switch that we use, with 3 banks of 8 ports (grouped for convenience/design more than anything else), had only 1 bank functioning. What a bother that turned out to be… Drove me up the wall trying to figure out what the problem was!