LOTS of spam getting through in last 2 weeks

Up until about 2 weeks ago, my Norton 360 Anti-Spam would filter out almost all the spam from my Outlook 2010 inbox, and I'd get maybe 5-10 spam emails a day.  Then, on Feb 19th (I can tell by looking at my junk email folder...prior to 2/19, almost all the emails show as not being viewed <the type is bold>, after 2/19,  50% of the emails in there have been manually flagged by me so they show up as being viewed <normal type>), I started getting a LOT of spam in my inbox!  I don't remember anything happening on that day, but the spam has been hot and heavy since then!

I contacted Norton Support, and after the tech tried to take control of my machine (which makes me nervous anyway), he sent me an email explaining how to disable the Anti-Spam integration and then re-enable it.  After that, I'm still getting probably 25-50 spam emails that I've got to manually mark as spam!  when I look in my junk email folder, it looks like 30-40% of the items in there have been manually marked by me.

Anyone have any idea why anti-spam stopped working well on or around 2/19?