One core jumps to 100% or all 6? Install Process Explorer and try to narrow down what process/thread is taking the cpu time: http://technet.microsoft.com/en-us
All 12 regular and virtual cores spike when it happens. After some messing around some I'm able to reproduce the issue when I need to. It will randomly occur when opening new windows or loading videos, but it seems to always occur when opening a new browser after being idle for several moments.
I used the program you recommended and the process "McSvHost.exe2392" is the culprit of the spikes. I Included some pictures below to help with further troubleshooting, but after a quick Google search of the process I don't know if it is part of my McAfee anti-virus software or malware.