Video is pausing/freezing up for approximately 250ms periodically every 1 to 1.5 seconds. This behavior is occurring in Flash and youtube across almost all websites. An exception: Netflix is not affected due to its buffering of the fast incoming signal.
As shown in the screenshot I have excellent internet connectivity: >100mbps with 1ms latency. These numbers were tested on both chrome and firefox. Note: the speedtest itself was getting the same pausing/freezing behavior - even while reporting up to 110mbps!
The cpu level is low < 20% and there is free RAM available on my core i7 2.3GHz 16GB retina display machine.
This behavior seems to briefly be mitigated after a fresh reboot: but soon continues again. Stopping/restarting the browsers (tried Chrome, safari, ff) has NO effect. The behavior has been ongoing for weeks at the least.