Yea, there is something screwy going on with Adblock Plus as of late. I went to one website where an advertisemant should have been blocked. Did a quick search for it through the blockable items, and I found that googleadservice, or one of those things, had been whitelisted/enabled when I know I had specifically made it forbidden/blocked. It was an actual pain when this "first" happened. I had to disable it completely, then re-enable the item to be blocked. There are times when i've actually had to go in through the open blockable items, click on some random item to select block this, then went to the custom area to type in the address to block said item.
Also, I do want to warn people that Adblock Plus is great, but it can get trounced. If you don't enable it with wildcards, things can slip through. One final note is that website will change up ad service providers. There's been one or two websites, where they'll switch up their providers and you have to find what the advertisemant is and then block it. Once you take the time to learn the ins and outs of ABP, it's a very powerful tool.