I've had the same problem, on occasion.
Can't help fix it, I'm afraid, but it did 'go away'.
For me, the problem surfaced when I upgraded Flash to a new version, not before!
In fact, Flash worked on some sites and not on others.
So, I put this down to a Flash problem, rather than Opera, but I'm not so savvy on these things.....
I tend to hold off on Flash upgrades now.