The hosts file wasn't converted from DOS to Unix for 0.6.2, which is why it's not working. You are correct that MIUI does not have an ad blocking script, but there is a workaround with ADB or Root Explorer. If you search for "MIUI ad blocking", you should find it, but it's basically as simple as copying over the hosts file in your etc directory with a modified one that includes common ad-generating sites. It literally takes two minutes to do. There's another workaround using Terminal Emulator in this forum, also, but I can't remember the ADB commands to save my life.