full system scan NIS 2011

Hello, new here and thanks so much for the help that is provided on here.

 

Have a question about full system scan and this has been going on since I have upgraded to Firefox 4.  While online and running a full system scan, I notice that some web pages load faster than others.  The only problem I encounter is while I am logged onto sites like Career Builder, pages load very slow and going back and forward is also very slow.  But just normal surfing from site to sites that I am not logged into, no issues.  I do not recall having this issue before Firefox 4, not sure if it is due to that.

Everything is up to date and I have Windows 7 64 bit, 8 gigs of ram and Inet Core I7 920 processor.  No other issues.

Thanks for any advice because love running NIS 2011.