This is specific to the Developer fork of Opera (I can't attest to the Beta version).
Since the last update, Opera will prevent access to any website, after an hour or so. Also, whenever I access an extension (be it via the icons in the toolbar or viewing the extensions list), Opera will freeze. I depend on extensions and absentmindedly use Tab Killer and Ghostery before realizing I have to Force Quit Opera in order to get back to what I was doing.

Also wanted to point out that this is Opera 29. Additionally, the memory usage is insane. I believe this is when Opera Developer freezes and refuses to close tabs. A force quit is required to exit.