How to speed up my computer during manual scan of NIS 2011

When I upgraded my NIS 2010 to NIS 2011, I found there were some improvements over the previous versions of norton, but when I started a manual scan (a complete scan for example), the PC ran out of resources and my CPU usage became 100% (although my CPU is AMD Phenom II X2 550) and my PC became extremely slow and may have become so unresponsive that I had to restart my computer.....So I had  to roll back to my previous NIS 2010.

Has anyone encountered such a problem?
Does anyone have a solution to this problem?(I hope I can find one!)


Thanks in advance.