it also happens to me and it doesn't matter what version it is. It seems to happen with all the blink-based Opera versions. For reference, I'm using Win 8.1 x64, Opera 26. I use Nod32 and Comodo firewall, but things seem to work fine with mozilla-based browsers and IE. After a while, blink-based browsers seem to halt the computer. You don't need to restart as it evenutally comes back, but process explorer or task manager will show 100% CPU and 100% disk usage attributed to no one process, but to the SYSTEM process.
it's odd and only reproducible after browsing for a period of time. I've noticed several other posts about the exact same thing, but it hasn't been seriously investigated for a solution.