Do they go to a patch panel and are they labeled so you can test them individually? Do you know if the ones gone bad might run through a common location? Perhaps over something that gets very hot? This might sound not to be possible but animals hiding in ceilings and other nooks and crannies of a building can damage wiring.
I am having problem with some of my network drops in my school network. Approximately 40 cable drops from the ceiling in classrooms have quit working all of a sudden. The other 60 or so seem to be working just fine. I can not seem to track down any other problem with the switches or the router. I have ran a network cable to an active drop which works just fine. I would not have a problem rerunning all of the cables except for the fact that I find it odd that several have gone out instead of just a few. Any advice would be greatly appreciated.