Why do my videos freeze sometimes?

This can have several reasons:

1. CPU overload of your computer (too many windows open in your browser, other Flash elements loaded parallel, other CPU-draining applications open)
    
2. Fluctuating internet connection (wireless connections, mobile connections, fluctuations within the networks of the Internet Service Provider, public hotspots, etc...)
    
3. Selecting a high quality for the video (select a lower video quality on the player)