As for high CPU usage yesterday,11/14/13, anyone using Semantic (Norton) might have been the cause.
They may have been working on their site yesterday morning into late afternoon. I had a "high usage" on one of my 8-cores yesterday morning. I am set up for alerts such as this (maybe a little paranoid). I turned off DSL, ran full scan and checked usage monitors.
Norton has your computer check for updates, reputation scans and checks, during the time on line. When I ran a reputation scan there were times connecting failed, or took longer working.
Things were working better yesterday evening, and everything normal this morning. As mentioned by someone else these protection programs can cause excess CPU usage, along with the computer's own check-out program on start-up.
No big deal on an i7 8-core computer but big problems on older or smaller systems.