Do you noticed you can actually play snake game by pressing the arrows key on your keyboard when buffering icon is showing?
No.. That's not the point.. 
I am using 1Mbps line and viewing 360p video on YouTube shouldn't be a problem to me (well I can't forward it). But recently 360p is unstable, a lot. 
So I searched across Internet and came to this little trick (solution).
It works for me although not very obviously. 
Basically the steps are:
1.   Open Command Prompt with admin priviledge
      (Start -> type in "cmd" -> right click "run as administrator")
2.   Copy the following 
       netsh advfirewall firewall add rule name="YourRuleName" dir=in action=block remoteip=173.194.55.0/24,206.111.0.0/16 enable=yes
3.    Paste into the Command Prompt. (CRTL + V won't works in CMD, right click -> paste instead)
4.    Enter and you shall see the message "Ok"
To revert, simply enter 
netsh advfirewall firewall delete rule name="YourRuleName"
 
