NIS ad-block not working after installing XP SP2

I use Windows XP and I installed Service Pack 2 about two weeks ago. Today I went online with the PC and I find that my trusted NIS 2008 is not blocking ads.
 
I see no indication of problems in NIS, everything is green and seemingly in order. Ad-block is on but it doesn't block any ads. Whatever I add to the filter is not blocking anything.
I have tried to turn ad-block off and on but to no help.
 
Is XP SP2 known for causing problems with NIS 2008 Add-On Pack?
 
The very reason I still use NIS 2008 is its ad-block.