Hello,
Could it be the result of interaction between your web browser, the Flash player and your security software? Perhaps the latter is trying to scan the incoming stream of data for malware, which is why the CPU utilization is so high. I would expect to see that in the components which make up the security software and not the Flash player, though.
If you have the ability to exclude the process or network stream from being scanned, you could try that and see if it makes any difference.
Regards,
Aryeh Goretsky