I added a few things to my hosts file for ad-blocking (doubleclick, etc), and Chrome has since started behaving oddly... The back button reloading the same page and adding another history element, etc.

Maybe due to javascript trying to call things that don't exist? Not sure. Just be aware that hosts blocking can cause odd page results on occasion, because of content fetch failures (as apposed to noscript/adblock which often stop the request from even happening).