Actually I have a similiar problem. Also Win 8.x 64bit. I realized it just freezes with certain pages (Facebook being one,der-postillion.com and ashwinder.sycophanthex.com others, all three work in Firefox). At first it starts off as a really long loading time and then turns into freezing opera and eventually the entire system.
Funny thing: I haven't changed a thing with opera except updating. It has only become this worse lately though.
Any ideas? I pretty lost with this, especially as my knowledge about computers is pretty basic. I tried clearing the cache first thing but it didn't help.