|It sounds like the switch itself may be failing.|
I have one at work that recently screwed up and ports 37 to 46 can't communicate with any even number ports from 2 to 36 but can communicate with the odd numbered ports in the same range. Ports 37 to 46 can communicate with each other just fine. Go figure! lol
So, you may have a couple of ports that have, for whatever reason, stopped communicating with each other.
Assuming your switch has 4, or more, ports, I would open a command prompt window on both of your computers and would ping each other (ie: PC 1 pings PC 2 and vice versa) and then see what happens. If you get no replies, then you're having a similar issue (ie: no communication between the two ports) and you can try (one at a time) moving the plugs from one port to another. If you find two ports that communicate, leave your PC's plugged into them. But, if this is the case, I would seriously consider buying a replacement. In fact, if it were me, I'd buy a SOHO router with 4 LAN ports.