DNS not resolving hosts on browser

Hello,

I'm having DNS resolution issues on browsers. I've tried everything and the only thing that worked (partially with slow resolution) was:

sudo dscacheutil -flushcache sudo killall -HUP mDNSResponder

I also tried the following but it didn't work:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist

I'm running OSX ML on Macbook Pro. This started only a couple days ago, and it has been annoying. Whether I do this over WiFi or wired connection, changing DNS servers (8.8.8.8 and 208.67.222.222), it doesn't fix it. I also tried browsing by IP and that worked. Torrent worked as well (because it connects to IPs usually, not hostnames).

The above solutions I posted came from this post (and thanks to CajunLuke for posting the answer that worked for me!)

I'd like some expert help please. Like the users in the post claimed, there's only restoring to defaults - but there has to be a reason why this happens, how to avoid it and how to solve it.

Thanks!