High CPU usage while buffering a video

I have a high CPU usage (over 40%) while only buffering this video.

IE10pre1

Firefox Nightly 20121229, protected mode enabled

Firefox Nightly 20121229, protected mode disabled

Opera Next

Chrome Canary

a) open this url: http://www.wimp.com/marsearth/

b) pause the video if it starts automatically

c) use task manager or process explorer to view the cpu/gpu usage

reproducible: mostly

Windows 7 SP1

Flash Player 11.6.602.108 / HWA enabled

TestPC: Gigabyte GA-K8NS Pro; AMD Athlon 64 Venice 3200+; 2x 1GB MDT DDR-400-CL2; Club3D HD4670 AGP; Samsung HD103SJ, SyncMaster 204BM