Certain websites are being blocked on my computer, can anyone help?

Over the past 12 hours, I have not been able to load Facebook or use the Last.fm scrobbler on my computer that inputs my plays into my account. It's only those two sites that are being blocked; everything else is loading properly. I've encountered these problems before, and last time, MSE was blocking my access, so I had to uninstall it. After that, everything went back to normal. I thought that was the problem this time because I recently installed AVG. Before doing that, though, I checked to make sure it wasn't the browser (it wasn't), checked to make sure everything was updated (it was), and ran a computer scan with AVG to ensure there weren't any serious threats blocking my access. The scan detected a few small threats, but nothing that I wouldn't normally find on a scan. I then decided that the only thing I really had left to try was uninstall AVG, which I did. I restarted my computer as I'd done earlier today multiple times, but the sites were still blocked. I'm not sure what to do at this point. Can anyone offer help? Thanks!