I am running Mythbuntu 12.04.5, and noticed that I was getting No warnings for a while, but because I had rarely used it for Internet, I didn't think much of it. However, after visiting a website that usually trips the sensors (CBS - Big Bang Theory), it came back with no warning, I looked deeper. I saw that no history was recorded, so I ran check-nr.sh and it said it was not running. I then tried running a number of net-responsibility commands and noticed that I received a significant amount of lines stating that the database was corrupt. In another thread I saw a way to "reset" by deleting the .db file as well as the config.xml and blacklist.xml.
It is now trying to download blacklist.xml and has been for about 20 minutes.