At work we had an FC3 system that had apparently undergone an abrupt reboot or power outage. After it came back up, the CPU usage was at 100%, so bad that I could not run top. Stopping httpd and nscd seemed to help make the system responsive, though udev kept working hard.
Deleting /var/run/nscd and /var/db/nscd, then rebooting seemed to help. Oddly enough, I restarted nscd after removing these files, and that seemed to have no effect. It wasn't until I rebooted that everything seemed to go back to normal.
Weird. Just wanted to throw that out to anyone out there having the same problem. Just delete your nscd DB files or folders and re-create the folders if necessary (Fedora's nscd init script does this automatically), then reboot.