I know it's been forever since I updated, though I've been thinking about it a lot. I have no excuses, but I thought a good place to get started again was with a well deserved shout-out to a blog called Malware Tips.
I have no idea how, because I never click on anything the least bit suspicious, but my computer had become infected with something. Every few minutes it was opening a new tab in my browser, and the site on the new tab would offer some sort of "computer cleaning service". Well, I obviously needed my computer cleaned up, but NOT by whatever entity was popping open these web pages!
I ran my anti-virus program and two well-known spyware/malware removers, but to no avail. I was getting very frustrated by the time I googled for help. Most of the pages that came up just told me to do all of the things I'd already done. ARGH! Then I found Stelian Pilici and his blog, Malware Tips. It had a whole page about exactly the problem I was having, which included a six-step action plan -- with screenshots for each step so that non-techies like me could understand it!
In less than 30 minutes, my problem was gone. The issue was fixed! So I shared Stelian's magic on my Google+, and also here on my blog. I will be a devoted follower of his blog and his G+ page going forward.
Thank you Stelian for your wonderful instructions! Without them, I'd probably still be pulling my hair out.