GSA keeps spiking from 10% CPU to 100% CPU.. Why?

I own one of the fastest dedicated servers available and usually my GSA is running at 10% or less CPU but occasionally it is spiking to 100% CPU which is causing a lot of problems and crashing of my DS.  I have GSA even set to only run 100 threads and it is still doing this CPU spiking.  What might be the possible cause of this?  By looking at the logs it appears to be spiking when it is loading url’s from the verified sites list but it also might be something else.  Any idea’s how to fix this?