Problems after last NIS update...

I have Norton Internet Security on two computers, Avast Anti Virus on another one.  After the last NIS version update I started having many problems with my PC's running on AMD processors, Windows 7.  Problems were with Google Chrome mainly.  Slow page loading, IE freezing, distortion of letters/lines, unable to open some pages, etc.  All of these were not happening before.  My PC running on Avast is not having any issues.  This became so bad that I had to uninstall NIS on one of the PC's and install Avast instead so I can use it.

Any ideas/solutions will be appreciated.  I like to keep NIS since I paid for the service, but can't use it now.