I'd think is likely either an extension, or the flash plugin. Usually the complaint is only Chrome freezing, but since your PC is actually freezing, it's more unusual.
Temporarily disable extensions to see if the behavior stops. If so, you can enable extensions until you find the culprit. Scroll down to Temporarily disable extensions Manage your extensions - Google Chrome Help
You might also try this flash fix that has been an issue with Chrome itself freezing on certain sites. How To: Solve your Google Chrome Freezing and Hanging Problems
If no help, I would open task manager Ctrl+ Shift+Esc
> Click on Options
> And click Always on top
Surf to an offending page and see if you can identify a suspect.