I had the same problem since version 32. I was so fed up with it that I was about to dump Opera. The only fix that works so far is to completely disable mouse gestures and use a different mouse gesture extension for chrome. So far, haven't seen a single lock up since. Something about the mouse gesture that is built into Opera is locking up and preventing any input. This often occurs on any web sites using Adobe Flash.
If it wasn't for the lack of updates for Coolnovo, I would have stayed with Coolnovo and dumped Opera a long time ago. Opera is barely usable only with adding about 5 to 6 extensions to enable simple Tab management options such as opening pages in a background tab, preventing the closing of application when the last tab has been closed, setting a new start page or replacing the crappy built-in speed dial software. Speed dial 2 is generations ahead of the garbage that Opera uses. Its sad how a great browser turned to crap by developers who doesn't listen to their own customers. They keep adding useless features and won't fix the things that makes browsing bearable by adding more tab browsing options. I hope they actually pay attention to the UI more instead of focusing on stupid changes like rewording "Opera" on the upper left corner to "Menu". Give me a break.