Flash is a separate process and would not be hitting the kernel this hard. If Flash was acting out of control, it would be your browser or a special contained Flash process in Activity Monitor.
what can be done in this case?
Have you tried using another browser instead of Opera? I found Opera to be rather cumbersome and slow when compared to Safari and Chrome. Besides, it's always a good idea to have more than one browser on hand for those times when problems occur.
Have you thought of updating the Flash plug-in for Opera?