Same problems here. Sites flicker and dissapear.
If I disable the adblocking some sites that previously dissapeared display, others still dont.
I did not perform any updates, opera just started this behaviour a couple of days ago, so what changed? Does the adblocker refer to an online database that since recently describes some pieces of code as ads (as someone noted: even opera.com wont load)?

I will study the instructions here and see if they work for me, but also I would like to understand what causes the problem, clearly more people are affected. Peace!
Mac OS X 10.8.5 64-bit