Question about background scans in NIS 2011

I'm having a problem with background scans starting even though the computer is not idle and using a lot of CPU.  Sometime CPU % goes high enough to trigger NIS' own performance monitor and warns about itself!  I've looked through the settings and don't see a way to adjust this behavior.  I would like the background scans to be low priority/cpu and not start when I'm using the computer.  If  that can't be acheived I would prefer to turn off the background scan feature, but I see no way to do this either.  Any help appreciated.